NMI watchdog: BUG: soft lockup - CPU#5 stuck for

Did not help.
But today I was on the server at this moment.
avg CPU usage was 50%. One CT with cpulimit 0.8 and cpuunits 8 start to use 100% of 1 core (see in top). load average was 200. When kill the process LA stay lower. Then again have high LA, and
NMI watchdog: BUG: soft lockup - CPU#5 stuck for...
 
Is it possible to convert LXC to OpenVZ?
- - -
Why you support so unstable virtualization like LXC and remove stable OpenVZ?
Very stupid decision! Sorry, but it's true.
 
Is it possible to convert LXC to OpenVZ?
- - -
Why you support so unstable virtualization like LXC and remove stable OpenVZ?
Very stupid decision! Sorry, but it's true.

OpenVZ project stopped and canceled their development, due to understandable reasons. therefore we are forced to remove it.

Your post indicates that you maybe missed some important facts.

And yes, LXC is much better suited for Proxmox VE in many parts.

See also:

https://pve.proxmox.com/wiki/Convert_OpenVZ_to_LXC