Firefox dropdown menus and toolbar popups inconsistently work
Both drop-down menus (e.g., the drop-down for "Which topic best describes your question?") and popup menus for add-ons in the bookmark bars work inconsistently or not at all. The right-click menu and the 3-bar menu often fail to work on the first few tries, but eventually open. (And in the case of the 3-bar menu, it often opens without certain options, like "Settings," "More tools," and "Help," though these usually appear after waiting a few seconds.) Other menus, like drop-down menus on website or several pop-ups for addons, don't work at all, no matter how many times I try.
The issue isn't solved by starting in Troubleshooting mode (insofar as they can be reproduced -- some things, like the add-on popups, can't be since the add-ons are disabled) or by clearing the cache.
I'm running Firefox Nightly 95.0a1 (2021-10-06) (64-bit) on Arch Linux, though the same issue seems to affect Firefox 93.0.
Thanks very much in advance for any help.