PSMDB connection issues with MongoDB

There are frequent Alerts going off in our Dev Cluster regarding MongoDB RepplicationSet Members. Which don’t seem to be able to connect to the main pod running it.

Some logs regarding this issue: psmdb connection problems - Pastebin.com

This seems to occur first in the backup-agent and then in mongod. Any ideas why this happens?
(K9s screenshot)

edit: some logs from mongodb-exporter which might be related

mongodb-exporter time="2022-08-01T14:30:27Z" level=error msg="Could not get MongoDB BuildInfo: server selection error: server selection timeout, current topology: { Type: Single, Servers: [{ Addr: 172.25.1.121:27017, Type: Unknown, State: Connected, Average RTT: 0, Last error: connection() : dial tcp 172.25.1.121:27017: connect: connection refused }, ] }!" source="connection.go:84"
mongodb-exporter time="2022-08-01T14:30:27Z" level=error msg="Problem gathering the mongo server version: server selection error: server selection timeout, current topology: { Type: Single, Servers: [{ Addr: 172.25.1.121:27017, Type: Unknown, State: Connected, Average RTT: 0, Last error: connection() : dial tcp 172.25.1.121:27017: connect: connection refused }, ] }" source="mongodb_collector.go:196"
mongodb-exporter time="2022-08-01T14:30:35Z" level=error msg="Could not get MongoDB BuildInfo: (KeyNotFound) Cache Reader No keys found for HMAC that is valid for time: { ts: Timestamp(1659363914, 1) } with id: 7088582426691108869!" source="connection.go:84"
mongodb-exporter time="2022-08-01T14:30:35Z" level=error msg="Problem gathering the mongo server version: (KeyNotFound) Cache Reader No keys found for HMAC that is valid for time: { ts: Timestamp(1659363914, 1) } with id: 7088582426691108869" source="mongodb_collector.go:196"