Kubuntu 24.04 with various Firefox iterations including 149.0.2. It happens on stand alone, snap and flatpak versions. I do not know what triggers this problem. As far as can tell it only occurs on Wayland and not on 'X'. .... After using Firefox normally for a while I first notice the problem when I can't click into the separate search box on the toolbar, then I find I can't drag the tabs around as per usual. Then, if I click on a toolbar icon it does not respond. In summary, the toolbar becomes inoperative. I do have 9 pinned tabs but I can often have many more standard tabs up before I ever notice the problem and, today, when it occurred I only had 3 additional tabs up. So, I can't tie the problem to the number of tabs.