Interface monitored on cluster keep getting marqued as stale

Hi,
I’ve used this blog post to set up a clustered monitoring of my proxmox nodes. Problem is, once the nodes’ interfaces are added to the cluster, they are permanently marked as “stale” on the monitoring interface and as “vanished services” in the service discovery interface, which results in a back and forth between the interfaces being discovered on the nodes and added to the cluster then being removed because they have “vanished”. What could be the problem?
Thanks.

CMK version: CRE 2.2.20p9
OS version: Debian 12