Opening this ticket here since I assume it might be a driver issue.
Since MacOS Catalina, mouse movement triggers keyup / keydown Events, which introduces functional bugs in certain modifications such as switching cmd and ctrl while keeping ctrl+tab / alt+tab unmodified.
Also see here: pqrs-org/Karabiner-Elements#2304
I put a bounty of 30EUR or USD, whatever you prefer, on a bugfix. I know it is not that much, but I'm only using this on my personal computer.