KDE 6 on Fedora 40 beta, but the case was same with F39 with KDE 5.27.xx. 1. Logitech Performance MX mouse with two extra buttons (beside back & forward ones). 2. Set those 2 buttons via KDE System Settings - Mouse - Bind Additional Mouse Buttons for: a) CTRL-W for closing a tab b) ALT-F4 for closing a window/program 3. At some point CTRL-W binding stops working, at least in Firefox. It seems the ALT-F4 continues to work. Seems like some focus problem, but I can select text in the active tab. Changing a tab does not fixes the issue. 4. It starts working again: a) after some time (could not determine any logic in it) b) after just opening KDE System Settings - Mouse - Re-Bind Additional Mouse Buttons window (do nothing, just open) Tested on two PC: notebook and desktop, using two different mouses. I'm a Linux beginner, can provide/do logs/tests if step-by-step guide is provided.
Can confirm now (just experienced it again): the ALT-F4 bounded button closes the whole window, but the CTRL-W bounded button stops working and resumes after some time (or changing some tabs?).
Just got it again. It is not FF related, in Thunberbird as well a tab would not close, as a Telegram window as well. Opened KDE System Settings - Mouse - Re-Bind Additional Mouse Buttons window and all works again OK: FF and TB tabs closes, Telegram windows closes as well.
Now I got it. When Russian keyboard layout is selected, the CTRL-W binding does not work. It works only with Latin bindings.
Same ALT+latin letter does not work when Russian keyboard layout is selected.
It works not only with English, but any Latin keyboard layout.