diff --git a/synchronization/src/main/java/de/cyface/synchronization/WiFiSurveyor.java b/synchronization/src/main/java/de/cyface/synchronization/WiFiSurveyor.java
index de48aa980..559f9a8a8 100644
--- a/synchronization/src/main/java/de/cyface/synchronization/WiFiSurveyor.java
+++ b/synchronization/src/main/java/de/cyface/synchronization/WiFiSurveyor.java
@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2021 Cyface GmbH
+ * Copyright 2017-2024 Cyface GmbH
  *
  * This file is part of the Cyface SDK for Android.
  *
@@ -49,8 +49,6 @@
  *
  * @author Klemens Muthmann
  * @author Armin Schnabel
- * @version 7.2.1
- * @since 2.0.0
  */
 public class WiFiSurveyor extends BroadcastReceiver {
 
@@ -374,8 +372,8 @@ public void makeAccountSyncable(@NonNull final Account account, boolean enabled)
      * @return The only <code>Account</code> existing
      */
     public Account getAccount() {
-        final AccountManager accountManager = AccountManager.get(context.get());
-        final Account[] cyfaceAccounts = accountManager.getAccountsByType(accountType);
+        final var accountManager = AccountManager.get(context.get());
+        final var cyfaceAccounts = accountManager.getAccountsByType(accountType);
         if (cyfaceAccounts.length == 0) {
             throw new IllegalStateException("No cyface account exists.");
         }
diff --git a/synchronization/src/main/kotlin/de/cyface/synchronization/AuthStateManager.kt b/synchronization/src/main/kotlin/de/cyface/synchronization/AuthStateManager.kt
index 79dad5c27..ee292566f 100644
--- a/synchronization/src/main/kotlin/de/cyface/synchronization/AuthStateManager.kt
+++ b/synchronization/src/main/kotlin/de/cyface/synchronization/AuthStateManager.kt
@@ -32,16 +32,10 @@ import java.util.concurrent.locks.ReentrantLock
  * This stores the instance in a shared preferences file, and provides thread-safe access and
  * mutation.
  */
-class AuthStateManager private constructor(context: Context) {
-    private val mPrefs: SharedPreferences
-    private val mPrefsLock: ReentrantLock
-    private val mCurrentAuthState: AtomicReference<AuthState>
-
-    init {
-        mPrefs = context.getSharedPreferences(STORE_NAME, Context.MODE_PRIVATE)
-        mPrefsLock = ReentrantLock()
-        mCurrentAuthState = AtomicReference()
-    }
+class AuthStateManager private constructor(private val context: Context) {
+    private val mPrefs: SharedPreferences = context.getSharedPreferences(STORE_NAME, Context.MODE_PRIVATE)
+    private val mPrefsLock: ReentrantLock = ReentrantLock()
+    private val mCurrentAuthState: AtomicReference<AuthState> = AtomicReference()
 
     @get:AnyThread
     val current: AuthState
diff --git a/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceAuthenticator.kt b/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceAuthenticator.kt
index 989a34ee6..c0b5c5fae 100644
--- a/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceAuthenticator.kt
+++ b/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceAuthenticator.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2018-2023 Cyface GmbH
+ * Copyright 2018-2024 Cyface GmbH
  *
  * This file is part of the Cyface SDK for Android.
  *
@@ -44,13 +44,11 @@ import kotlinx.coroutines.runBlocking
  *
  * @author Klemens Muthmann
  * @author Armin Schnabel
- * @version 5.1.1
- * @since 2.0.0
  */
 class CyfaceAuthenticator(private val context: Context) :
     AbstractAccountAuthenticator(context), LoginActivityProvider {
 
-    private var auth: OAuth2 = OAuth2(context, settings)
+    var auth: OAuth2 = OAuth2(context, settings, "CyfaceAuthenticator")
 
     override fun editProperties(
         response: AccountAuthenticatorResponse,
diff --git a/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceAuthenticatorService.kt b/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceAuthenticatorService.kt
index 24248d9f3..049a58d9b 100644
--- a/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceAuthenticatorService.kt
+++ b/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceAuthenticatorService.kt
@@ -21,7 +21,6 @@ package de.cyface.synchronization
 import android.app.Service
 import android.content.Intent
 import android.os.IBinder
-import android.util.Log
 
 /**
  * The Android service used to communicate with the Stub Authenticator. This has been implemented as described in
@@ -29,8 +28,6 @@ import android.util.Log
  *
  * @author Klemens Muthmann
  * @author Armin Schnabel
- * @version 1.0.7
- * @since 2.0.0
  */
 class CyfaceAuthenticatorService : Service() {
     /**
diff --git a/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceSyncService.kt b/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceSyncService.kt
index 50b485e8c..538efe679 100644
--- a/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceSyncService.kt
+++ b/synchronization/src/main/kotlin/de/cyface/synchronization/CyfaceSyncService.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2017-2023 Cyface GmbH
+ * Copyright 2017-2024 Cyface GmbH
  *
  * This file is part of the Cyface SDK for Android.
  *
@@ -34,8 +34,6 @@ import kotlinx.coroutines.runBlocking
  *
  * @author Armin Schnabel
  * @author Klemens Muthmann
- * @version 1.0.9
- * @since 2.0.0
  */
 class CyfaceSyncService : Service() {
 
@@ -46,7 +44,7 @@ class CyfaceSyncService : Service() {
                 syncAdapter = SyncAdapter(
                     applicationContext,
                     true,
-                    OAuth2(applicationContext, CyfaceAuthenticator.settings),
+                    OAuth2(applicationContext, CyfaceAuthenticator.settings, "CyfaceSyncService"),
                     DefaultUploader(collectorApi),
                 )
             }
diff --git a/synchronization/src/main/kotlin/de/cyface/synchronization/OAuth2.kt b/synchronization/src/main/kotlin/de/cyface/synchronization/OAuth2.kt
index 1acca884b..e584f5128 100644
--- a/synchronization/src/main/kotlin/de/cyface/synchronization/OAuth2.kt
+++ b/synchronization/src/main/kotlin/de/cyface/synchronization/OAuth2.kt
@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 Cyface GmbH
+ * Copyright 2023-2024 Cyface GmbH
  *
  * This file is part of the Cyface SDK for Android.
  *
@@ -22,7 +22,6 @@ import android.accounts.Account
 import android.accounts.AccountManager
 import android.content.ContentResolver
 import android.content.Context
-import android.content.Intent
 import android.os.Build
 import android.os.Bundle
 import android.util.Log
@@ -38,7 +37,6 @@ import net.openid.appauth.AuthState
 import net.openid.appauth.AuthorizationException
 import net.openid.appauth.AuthorizationResponse
 import net.openid.appauth.AuthorizationService
-import net.openid.appauth.AuthorizationServiceConfiguration
 import net.openid.appauth.ClientAuthentication
 import net.openid.appauth.EndSessionRequest
 import net.openid.appauth.TokenRequest
@@ -52,12 +50,10 @@ import org.json.JSONObject
  * accounts, and handling sessions.
  *
  * @author Armin Schnabel
- * @version 1.0.0
- * @since 7.9.0
  * @param context The context to load settings and accounts from.
  * @param settings The settings which store the user preferences.
  */
-class OAuth2(context: Context, settings: SynchronizationSettings) : Auth {
+class OAuth2(context: Context, settings: SynchronizationSettings, caller: String) : Auth {
 
     /**
      * The service used for authorization.
@@ -67,23 +63,21 @@ class OAuth2(context: Context, settings: SynchronizationSettings) : Auth {
     /**
      * The authorization state.
      */
-    private var stateManager: AuthStateManager
+    private var stateManager: AuthStateManager = AuthStateManager.getInstance(context)
 
     /**
      * The configuration of the OAuth 2 endpoint to authorize against.
      */
-    private var configuration: Configuration
+    private var configuration: Configuration = Configuration.getInstance(context, settings)
 
     init {
-        // Authorization
-        stateManager = AuthStateManager.getInstance(context)
-        configuration = Configuration.getInstance(context, settings)
         /*if (config.hasConfigurationChanged()) {
             //throw IllegalArgumentException("config changed (SyncAdapter)")
             Toast.makeText(context, "Ignoring: config changed (SyncAdapter)", Toast.LENGTH_SHORT).show()
             //Handler().postDelayed({signOut()}, 2000)
             //return
         }*/
+        Log.i(TAG, "OAuth2 init ($caller)")
         authService = AuthorizationService(
             context,
             AppAuthConfiguration.Builder()
@@ -259,7 +253,7 @@ class OAuth2(context: Context, settings: SynchronizationSettings) : Auth {
     fun signOut() {
         // discard the authorization and token state, but retain the configuration and
         // dynamic client registration (if applicable), to save from retrieving them again.
-        val currentState: AuthState = stateManager.current
+        val currentState = stateManager.current
         if (currentState.authorizationServiceConfiguration != null) {
             // Replace the state with a fresh `AuthState`
             val clearedState = AuthState(currentState.authorizationServiceConfiguration!!)
@@ -267,16 +261,26 @@ class OAuth2(context: Context, settings: SynchronizationSettings) : Auth {
                 clearedState.update(currentState.lastRegistrationResponse)
             }
             stateManager.replace(clearedState)
+
+            // [LEIP-233] Completely deleting the sharedPreferences/AuthState.xml file does not
+            // fix the `Credentials incorrect` error after re-login (app restart required)
+            //stateManager.deletePreferencesFile()
+        } else {
+            Log.w(TAG, "No authorization service configuration to sign out")
         }
+
+        // Invalidate all tokens to ensure they are no longer used
+        dispose()
     }
 
-    // Keep: login is currently just deactivated because it's buggy
+    /**
+     * Sends the end session request to the auth service to sign out the user.
+     */
     fun endSession(activity: FragmentActivity) {
-        val currentState: AuthState = stateManager.current
-        val config: AuthorizationServiceConfiguration =
-            currentState.authorizationServiceConfiguration!!
+        val currentState = stateManager.current
+        val config = currentState.authorizationServiceConfiguration!!
         if (config.endSessionEndpoint != null) {
-            val endSessionIntent: Intent = authService.getEndSessionRequestIntent(
+            val endSessionIntent = authService.getEndSessionRequestIntent(
                 EndSessionRequest.Builder(config)
                     .setIdTokenHint(currentState.idToken)
                     .setPostLogoutRedirectUri(configuration.endSessionRedirectUri)
@@ -310,4 +314,4 @@ class OAuth2(context: Context, settings: SynchronizationSettings) : Auth {
                 .put("https_required", true)
         }
     }
-}
\ No newline at end of file
+}