[prometheus-kube-stack] Provision alertmanager configuration: failed to initialize from secret

[gabriel-suela]

Describe the bug a clear and concise description of what the bug is.

I'm receiving this error on prometheus stack operator and cannot find any solutions or clues about it.

{"ts":"2025-01-13T12:55:52.916624125Z","level":"error","caller":{"function":"github.com/prometheus-operator/prometheus-operator/pkg/operator.(*ResourceReconciler).processNextReconcileItem","file":"/workspace/pkg/operator/resource_reconciler.go","line":557},"msg":"Unhandled Error","logger":"UnhandledError","err":"sync \"monitoring/kube-prometheus-stack-alertmanager\" failed: provision alertmanager configuration: failed to initialize from secret: yaml: unmarshal errors:\n  line 48: cannot unmarshal !!map into []string"}

What's your helm version?

v3.15.3

What's your kubectl version?

v1.30.3

Which chart?

prometheus-stack

What's the chart version?

67.11.0

What happened?

No response

What you expected to happen?

No response

How to reproduce it?

No response

Enter the changed values of values.yaml?

No response

Enter the command that you execute and failing/misfunctioning.

.

Anything else we need to know?

No response