Windows and bookmarks dropped on bootup

Dell Optiplex desktop, Linux Mint Mate 22 OS. Currently updated to FF 150.0. For several months, this machine has failed to load bookmarks, approximately half the time. Banner message displayed advising user to load bookmarks. Closing and restarting FF usually (but not always) corrects this. Also, last month or so, bootup displays single window, even if there were two or more on previous shutdown. In settings menu, FF is set to re-open previous windows and tabs. Also on boot, this machine takes much longer to open FF than an older Dell Inspiron laptop, which is otherwise slower than this desktop. When FF icon selected in desktop, just before it opens, the tray flashes the missing extra window but it is not shown or available in the tray and does not load.

The two machines are set up identically, both in FF settings and with the same add-ons- Privacy Badger and uBlock Origin. Just looked in Synaptic of both machines and the laptop shows two FF items as installed- FF 150.0 +linuxn The FF Web Browser and FF-en locale English language pack. The desktop Synaptic shows no FF items installed (!). The laptop runs as expected, opening FF with all windows and bookmarks. Both machines received FF 150.0 via update manager.