Alertmanager is in crashloopback due to caller=main.go:218 err="invalid state"

Issue

The alertmanager shows information as invalid state:

[root@master1 ~]# oc logs -n openshift-monitoring alertmanager-main-1 -c alertmanager
level=info ts=yyyy-mm-dTHH:MM:ss.00000Z caller=main.go:174 msg="Starting Alertmanager" version="(version=0.15.2, branch=, revision=)"
level=info ts=yyyy-mm-dTHH:MM:ss.00000Z caller=main.go:175 build_context="(go=go1.10.8, user=mockbuild@x86-034.build.eng.bos.redhat.com, date=20190609-23:44:21)"
level=error ts=yyyy-mm-dTHH:MM:ss.00000Z caller=main.go:218 err="invalid state"

Indicating data corruption on the PVC