C4 "stops working" after some minutes

I am unable to relate my ‘problem’ to other posts, sorry in case I overlooked relevant ones.

Had installed build 1064 a while ago and 1150 this week to see whether the problem persists. It seems to.
I installed C4 on a rather recent, fairly powerful laptop (a 2022 hp spectre 360, Win11) with a less recent audio interface (motu 828 mkII), and up to three midi keybords connected. It took a while but got it going.
However, after some minutes of playing, part of the system stops working. Symptoms are as follows:
(1) pressing keys on the keyboards gives a flashing green indicator on the general “inputs” indicator, but those of the individual keyboards (MIDI in and out) remain pale white/inactive.
(2) this nonwithstanding I can still double click on plugins and play on their controls.
(3) The metronome wouldn’t play any more the play button goes green but no sounds, no counting of measures or beats. Pressing pause/stop seems to work like expected on the GUI level but the metronome remains inactive.

Varikus ways of ending and restarting C4 do not change the situation unless I reboot the computer. Upon rebooting I can start over and play on keys and with the metronome - but just for a few minutes again.
Have tried with several plugins, 2 that came with a cakewalk (unregistered, maybe have restrictions), two for which I have brand new iLok licences and the Modal Cobalt8 plugin. Same basic problem (with Modal, C4 crashed after a while).
If I am not mistaken, all these are VST3type plugins.

Any ideas?
Thanks for any willingness to help a total newbie. Will try on a different laptop next (older Dell M3800, Win 8.1)

Additional question: do I need a new C4 license code to try this on another computer?