All I did was:I installed your addon jsut to see if it happened.
And it did without being in a group. I need to nail down wich other screens can cause this.
I cannot reproduce it even by following the steps precisely, so it might be realted to some Reserach Start traking addon.
ESC also becomes unuseable whenever:
Add d() messages to every function and especially events handlers (start and end)
Use BugEater wit henamebeld pre-init debug (needs only be optional dependency) to get d() messages from around Addon Load Event
Double and tripple check that you do not use any Global variables anywhere, unelss you really need them.