Some WSLg windows apparently ignore the mouse

(This is a bit of a Big Wall Of Text; my actual questions are boldfaced, but unfortunately the surrounding text is probably needed to make sense of them.) I am running WSL2 under Windows 11. (WSL version 2.0.0.0, WSLg version 1.0.57, Ubuntu 20.04.6 LTS installed IIRC via the Microsoft Store.) From time to time I observe the following strange behaviour. (I shall describe the way it's behaving right now , which I can observe closely; I am fairly sure I have seem similar symptoms before but I cannot guarantee that they were exactly the same.) Some but not all of the GUI windows I have created fro

Question by Gareth McCaughan on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.