hello mpoirier101, unfortunately this is currently a bug in the current firefox version when you have set your history to be cleared at firefox shutdown under options > privacy - that problem is investigated and in the process of getting fixed by mozilla's developers.

From what I have been reading from other posts on this forum, the issue may be caused by the clear history settings.

Press the <Alt> or <F10> key to bring up the tool bar. Then Tools > Options > Privacy. The button next to History, select Use Custom Settings.

At the bottom of the page, turn on Clear History When Firefox Closes. At the far right, press the Settings button. Turn on ONLY Cache and Form And Search History leaving the others off.

This is not a cure but will make it easier if Firefox locks up. https://support.mozilla.org/questions/997866?esab=a&s=&r=1&as=s {web link}