Audio clipping/skipping when tracks are being played (C11)?

When I try to play tracks audio stops several times and jumps randomly forward skipping audio which jeopadize e.g. record vocal to a track.

“Processing overload” turns high and red light even when idle (no effect whether play stopped or started).

I have upgraded PC with 16 GB RAM without any significant change.

Furthermore since upgrade to C10.5 and then C11:

  • I am no longer able to have more than a few tracks.
  • I had to remove almost all my 3rd party plugins - no longer able to mix as normal.
  • When export to wave file no problems occurs.

Is this problem the same on C12?

DAW platform: Cubase PRO 11, Lenovo Ideapad 330 Laptop, Windows 11 Home, processor: Intel(R) Core™ i5-8250U CPU @ 1.60GHz 1.80 GHz, RAM 20 GB.