Hi, I had two similar issues (although they are related to Cubase 14…)
(1) Do you have a MIDI remote control? Which one is it? I had issues with Cubase 14 and Novation Lunchpad 25. Disabling the MIDI remote control completely solved the problem. The syndrom was, for that reason or another, similar to what you described.
(2) I am now having a (new, recent) issue with cubase 14, where after awhile (especially when I play MIDI), it starts to pause for short periods upon UI manipulations (e.g., selecting a different track in the project window, using the horizontal scroll bar of MixConsole, or even doing switching to other applications. Right now, I’m still debugging this issue (it’s not happening immediately, and not always…) but at least dynamically changing the affinity to P-Cores only is doing good things. (Anyways if you try that - don’t overlook the “force mode” in process lasso (see my comment that @starnaf just added to this thread)