diff --git a/src/domain-services/categories/category-service.ts b/src/domain-services/categories/category-service.ts
index 20560423..c64c54b4 100644
--- a/src/domain-services/categories/category-service.ts
+++ b/src/domain-services/categories/category-service.ts
@@ -57,7 +57,10 @@ export class CategoryService {
         throw new Error(`Category with ID ${catRef.categoryID} does not exist`);
       }
 
-      categoriesPerFlow.push(this.mapCategoryToFlowCategory(category, catRef));
+      if (!categoriesPerFlow.some((cat) => cat.id === category.id.valueOf())) {
+        const mappedCategory = this.mapCategoryToFlowCategory(category, catRef);
+        categoriesPerFlow.push(mappedCategory);
+      }
     }
 
     return categoriesMap;
diff --git a/src/domain-services/flows/flow-search-service.ts b/src/domain-services/flows/flow-search-service.ts
index 71a60111..c6d4f58d 100644
--- a/src/domain-services/flows/flow-search-service.ts
+++ b/src/domain-services/flows/flow-search-service.ts
@@ -147,7 +147,7 @@ export class FlowSearchService {
         const flowLink = flowLinksMap.get(flow.id) ?? [];
         const categories = categoriesMap.get(flow.id) ?? [];
         const organizations = organizationsMap.get(flow.id) ?? [];
-        const locations = [...(locationsMap.get(flow.id) ?? [])];
+        const locations = locationsMap.get(flow.id) ?? [];
         const plans = plansMap.get(flow.id) ?? [];
         const usageYears = usageYearsMap.get(flow.id) ?? [];
         const externalReferences = externalReferencesMap.get(flow.id) ?? [];
@@ -431,12 +431,11 @@ export class FlowSearchService {
       usageYears,
       childIDs,
       parentIDs,
-      origAmount: flow.origAmount ? flow.origAmount.toString() : '',
-      origCurrency: flow.origCurrency ? flow.origCurrency.toString() : '',
+      origAmount: flow.origAmount ? flow.origAmount.toString() : null,
+      origCurrency: flow.origCurrency ? flow.origCurrency.toString() : null,
       externalReferences,
       reportDetails,
-      parkedParentSource:
-        parkedParentSource.length > 0 ? parkedParentSource : null,
+      parkedParentSource,
       // Paged item field
       cursor: flow.id.valueOf(),
     };
diff --git a/src/domain-services/flows/graphql/types.ts b/src/domain-services/flows/graphql/types.ts
index 1307e47f..cfa313bb 100644
--- a/src/domain-services/flows/graphql/types.ts
+++ b/src/domain-services/flows/graphql/types.ts
@@ -61,41 +61,41 @@ export class BaseFlow extends BaseType {
 
 @ObjectType()
 export class Flow extends BaseFlow {
-  @Field(() => [Category], { nullable: true })
+  @Field(() => [Category], { nullable: false })
   categories: Category[];
 
-  @Field(() => [Organization], { nullable: true })
+  @Field(() => [Organization], { nullable: false })
   organizations: Organization[];
 
-  @Field(() => [BasePlan], { nullable: true })
+  @Field(() => [BasePlan], { nullable: false })
   plans: BasePlan[];
 
-  @Field(() => [BaseLocation], { nullable: true })
+  @Field(() => [BaseLocation], { nullable: false })
   locations: BaseLocation[];
 
-  @Field(() => [UsageYear], { nullable: true })
+  @Field(() => [UsageYear], { nullable: false })
   usageYears: UsageYear[];
 
-  @Field(() => [Number], { nullable: true })
+  @Field(() => [Number], { nullable: false })
   childIDs: number[];
 
-  @Field(() => [Number], { nullable: true })
+  @Field(() => [Number], { nullable: false })
   parentIDs: number[];
 
-  @Field({ nullable: true })
-  origAmount: string;
+  @Field(() => String, { nullable: true })
+  origAmount: string | null;
 
-  @Field({ nullable: true })
-  origCurrency: string;
+  @Field(() => String, { nullable: true })
+  origCurrency: string | null;
 
-  @Field(() => [FlowExternalReference], { nullable: true })
+  @Field(() => [FlowExternalReference], { nullable: false })
   externalReferences: FlowExternalReference[];
 
-  @Field(() => [ReportDetail], { nullable: true })
+  @Field(() => [ReportDetail], { nullable: false })
   reportDetails: ReportDetail[];
 
-  @Field(() => [FlowParkedParentSource], { nullable: true })
-  parkedParentSource: FlowParkedParentSource[] | null;
+  @Field(() => [FlowParkedParentSource], { nullable: false })
+  parkedParentSource: FlowParkedParentSource[];
 }
 
 @ObjectType()
diff --git a/src/domain-services/location/location-service.ts b/src/domain-services/location/location-service.ts
index eb83dbe0..cb6311da 100644
--- a/src/domain-services/location/location-service.ts
+++ b/src/domain-services/location/location-service.ts
@@ -33,7 +33,7 @@ export class LocationService {
   async getLocationsForFlows(
     locationsFO: Array<InstanceDataOfModel<Database['flowObject']>>,
     models: Database
-  ): Promise<Map<number, Set<BaseLocation>>> {
+  ): Promise<Map<number, BaseLocation[]>> {
     const locationObjectsIDs: LocationId[] = locationsFO.map((locFO) =>
       createBrandedValue(locFO.objectID)
     );
@@ -47,20 +47,26 @@ export class LocationService {
         },
       });
 
-    const locationsMap = new Map<number, Set<BaseLocation>>();
+    const locationsMap = new Map<number, BaseLocation[]>();
 
     for (const locFO of locationsFO) {
       const flowId = locFO.flowID;
       if (!locationsMap.has(flowId)) {
-        locationsMap.set(flowId, new Set<BaseLocation>());
+        locationsMap.set(flowId, []);
       }
       const location = locations.find((loc) => loc.id === locFO.objectID);
 
       if (!location) {
         throw new Error(`Location with ID ${locFO.objectID} does not exist`);
       }
-      const locationMapped = this.mapLocationsToFlowLocations(location, locFO);
-      locationsMap.get(flowId)!.add(locationMapped);
+      const locationsPerFlow = locationsMap.get(flowId)!;
+      if (!locationsPerFlow.some((loc) => loc.id === location.id)) {
+        const locationMapped = this.mapLocationsToFlowLocations(
+          location,
+          locFO
+        );
+        locationsPerFlow.push(locationMapped);
+      }
     }
     return locationsMap;
   }
diff --git a/src/domain-services/organizations/organization-service.ts b/src/domain-services/organizations/organization-service.ts
index 411531c4..2a73dae0 100644
--- a/src/domain-services/organizations/organization-service.ts
+++ b/src/domain-services/organizations/organization-service.ts
@@ -32,13 +32,17 @@ export class OrganizationService {
         );
       }
 
-      const organizationMapped: Organization =
-        this.mapOrganizationsToOrganizationFlows(
-          organization,
-          orgFO.refDirection
-        );
-
-      organizationsMap.get(flowId)!.push(organizationMapped);
+      const organizationPerFlow = organizationsMap.get(flowId)!;
+      if (
+        !organizationPerFlow.some((org) => org.id === organization.id.valueOf())
+      ) {
+        const organizationMapped: Organization =
+          this.mapOrganizationsToOrganizationFlows(
+            organization,
+            orgFO.refDirection
+          );
+        organizationsMap.get(flowId)!.push(organizationMapped);
+      }
     }
 
     return organizationsMap;
diff --git a/src/domain-services/plans/plan-service.ts b/src/domain-services/plans/plan-service.ts
index f4d98301..d7aaa617 100644
--- a/src/domain-services/plans/plan-service.ts
+++ b/src/domain-services/plans/plan-service.ts
@@ -74,24 +74,33 @@ export class PlanService {
         },
       });
 
-      const planFlowOobject = plansFO.find(
+      const planFlowObject = plansFO.find(
         (planFO) => planFO.objectID === plan.id
       );
 
-      const flowId = planFlowOobject && planFlowOobject.flowID;
+      if (!planVersion.length) {
+        throw new Error(`Plan with ID ${plan.id} does not have a version`);
+      }
 
-      const planMapped = this.mapPlansToFlowPlans(
-        plan,
-        planVersion[0],
-        planFlowOobject?.refDirection ?? null
-      );
+      if (!planFlowObject) {
+        throw new Error(`Plan with ID ${plan.id} does not have a flow object`);
+      }
+
+      const flowId = planFlowObject && planFlowObject.flowID;
+
+      if (!plansMap.has(flowId)) {
+        plansMap.set(flowId, []);
+      }
 
-      if (flowId) {
-        if (!plansMap.has(flowId)) {
-          plansMap.set(flowId, []);
-        }
+      const plansPerFlow = plansMap.get(flowId)!;
 
-        plansMap.get(flowId)!.push(planMapped);
+      if (!plansPerFlow.some((plan) => plan.id === plan.id)) {
+        const planMapped = this.mapPlansToFlowPlans(
+          plan,
+          planVersion[0],
+          planFlowObject?.refDirection ?? null
+        );
+        plansPerFlow.push(planMapped);
       }
     }
 
diff --git a/src/domain-services/report-details/report-detail-service.ts b/src/domain-services/report-details/report-detail-service.ts
index 9d0f898a..b7ef5533 100644
--- a/src/domain-services/report-details/report-detail-service.ts
+++ b/src/domain-services/report-details/report-detail-service.ts
@@ -30,10 +30,19 @@ export class ReportDetailService {
         (report) => report && flowId === report?.flowID
       );
 
-      if (reportDetail) {
+      if (!reportDetail) {
+        throw new Error(`Report detail with flow ID ${flowId} does not exist`);
+      }
+
+      const reportDetailsPerFlow = reportDetailsMap.get(flowId)!;
+      if (
+        !reportDetailsPerFlow.some(
+          (report) => report.id === reportDetail.id.valueOf()
+        )
+      ) {
         const reportDetailMapped =
           this.mapReportDetailsToFlowReportDetail(reportDetail);
-        reportDetailsMap.get(flowId)?.push(reportDetailMapped);
+        reportDetailsPerFlow.push(reportDetailMapped);
       }
     }
 
diff --git a/src/domain-services/usage-years/usage-year-service.ts b/src/domain-services/usage-years/usage-year-service.ts
index dfb1e6f5..7a495460 100644
--- a/src/domain-services/usage-years/usage-year-service.ts
+++ b/src/domain-services/usage-years/usage-year-service.ts
@@ -35,11 +35,14 @@ export class UsageYearService {
           `Usage year with ID ${usageYearFO.objectID} does not exist`
         );
       }
-      const usageYearMapped = this.mapUsageYearsToFlowUsageYears(
-        usageYear,
-        usageYearFO.refDirection
-      );
-      usageYearsMap.get(flowId)!.push(usageYearMapped);
+      const usageYearsPerFlow = usageYearsMap.get(flowId)!;
+      if (!usageYearsPerFlow.some((uYear) => uYear.year === usageYear.year)) {
+        const usageYearMapped = this.mapUsageYearsToFlowUsageYears(
+          usageYear,
+          usageYearFO.refDirection
+        );
+        usageYearsPerFlow.push(usageYearMapped);
+      }
     }
 
     return usageYearsMap;