I am glad it is solved on your side. After having discussed with upstream about this issue, there was no obvious culprit.
I believe, I am having the same issue. Sometimes, Firefox and Thunderbird freeze completely when you try to open a menu of an HTML combobox. The application need to be killed. But even after restarting the application, it is still not possible to open a menu. I reproduces the issue with: * firefox, firefox-esr from Debian testing; * firefox-esr firefox-esr from Debian testing; * Firefox, Firefox Nightly and Firefox Developer edition downloaded from Mozilla. * Thunderbird downloaded from thunderbird.net. This is not reliably reproducible, it only happens from time to time. once it starts happening, restarting the application does not fix the problem and all the affected applications are affected at the same time. What does not fix the issue: * restarting the application. What fixes the issue: * restarting the system; * killing wireplumber; * killing and restarting wireplumber. Configuration: * Debian testing; * wireplumber with the "combined sink" plugin enabled (I will try to see if this happens without this plugin); * pipewire, wireplumber, pipewire-alsa, pipewire-pulse; * X11, XFCE. Gabriel
