Tab Groups disappear when Firefox session is closed.

Windows 11 expensive high performance tower PC. When I am closing Firefox I am warned that I am about to close 80+ tabs although. I actually had only 13 tab groups (closed) and one ordinary tab open (The New York Times) I close Firefox anyway and ALL the group tabs disappeared. Sometimes, when I am warned that I am closing 80+ tabs, they luckily they haven't disappeared upon restarting Firefox. This happens often. I know how to reconstruct my tab Groups proceeding from listing all tabs. Sometimes the tab groups don't disappear. It makes no difference whether I start a Firefox session on my just rebooted PC (and run PC for a minutes only using Firefox) or not. When I recently closed Firefox I could see from task manager that there was minor activity showing in the Firefox app which surprised me. I hope you have an idea of what might be occurring. I'm not a novice, I purchased my first PC in 1989 Thank you, Anita ''Moderator note: This question has been edited to fix the formatting.''