OPNsense on Proxmox Freezing Every Few Nights

[misery]

 ::)
Intel NUC is affected, too.

[Jetro]

I'm running OPNSense (last version) on Proxmox without this problem, at home on a PowerEdge T20 (Xeon E3 1271 v3, 32GB, SSD) and at Work on a PowerEdge T440 (Xeon Silver 4110 x2, 256GB, 15k SCSI HDDs), also on another site in a PC (i5 6500, 16GB, SSD).
I think it could be hardware related? In my home setup, the T20, I have an Intel dual SFP+ for LAN and an Intel quad Gigabit for WAN(s),  no GPU, 1xSSD and the host is running 4 VMs and 3 CT with RAM constantly near 90% (I'm actually on ZFS, planning to switch back to ext4 to free up some RAM).