Same problem here (proxmox 6.2).
Only the VM with NFS (v4) have the issue, no problem with local storage or iscsi.
The memory grow fast when there are high IO on the disk.
Seems to be the same bug here: https://forum.proxmox.com/threads/error-clone-failed-command-sbin-lvs-separator-noheadings-got-timeout.52519/#post-261766
I've the same issue.
It's on a fresh proxmox 6.0, up to date (6.0.5). The HDD is an hardware RAID 1.
I've created only one VM and convert it to template. No other VM exist, only the single template and i can't clone it
The last line of the GUI:
in journalctl: