I’ve been using Manjaro for about a year, it’s perfect especially compared to Ubuntu. Everything was fine, but about half of an year ago (I’d been waiting for issue to be fixed by an update, but seems it won’t be) I noticed that when I holding left mouse button i.e. click mouse on desktop or any window (doesn’t matter) and hold mouse and than move the mouse. It’s released (while I’m holding button). On desktop it’s revealed by jumping selection rectangle while moving. The most annoying thing is that when I want to drag window or resize it or select a text the mouse releases. And I need to repeat couple of times to achieve what I want. After that issue disappears, but than accidentally reveals again, especially on window switch. I use latte dock (if it matters).
plasmashell --version
plasmashell 5.21.2