Inadequate memory usage

Hi,
in my homelab I’m running 2 USC server as primary- and backup node in a VM on two proxmox servers.
The primary node is fine w/ less than 3 GB RAM, but the backup node is going weired:
image
The memory consumption is ramping up, followed by CPU-utilization I cannot explain myself. Both goes normal when the server is beeing restarted.
This only happens on the backup node. Beside the Samba AD/DC only the software installation monitor is installed from the App-Center.

On the shell, htop is showing only one service utilizing ca. 16.0% of memory:
samba: task[drepl] pre-fork master
On the primary node this service is utilizing 0.8% of memory.

Can this be the root cause? Why are the the memory utilization different on the nodes?

Thanks for your help.

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