OK, good to hear and fingers crossed. I will try to get back to the
original problem and a better solution sometimes early next year when
all the things settle a bit.

Btw, i noticed one more thing when problem is happening (=when any cgroup is stucked), i fogot to mention it before, sorry :( . It's related to HDDs, something is slowing them down in a strange way. All services are working normally and i really cannot notice any slowness, the only thing which i noticed is affeceted is our backup software ( www.Bacula.org ). When problem occurs at night, so it's happening when backup is running, backup is extremely slow and usually don't finish until i kill processes inside affected cgroup (=until i resolve the problem). Backup software is NOT doing big HDD bandwidth BUT it's doing quite huge number of disk operations (it needs to stat every file and directory). I believe that only speed of disk operations are affected and are very slow.

Merry christmas!