In fairness to KDE, yes, VMs absolutely can cause issues, and it’s likely you’d experience fewer of them if you ran it on real hardware.
But yeah, Plasma is relatively buggy. This is improving at a rapid rate, though - Plasma 4 and early Plasma 5 were straight up unusable, hence distros flocking to Gnome (KDE actually used to be the standard!)
The difference in stability between Plasma 5.27 and versions before about 5.16 is night and day. And Plasma 6 has been repeatedly pushed back so that it can be stable from the get-go.