are the urls recorded under Menu History?

I mean all the history is still there but would be impossible to figure out what tabs I had opened had over a 100 opened. But no option to restore tabs all grayed out

It's hard to know what may be causing the issue because people load up all kinds of extra software on their windows, like anti-virals and scanners for this and that, plus also add things to firefox.

however, it is not to say that maybe FF doesnt have a bug as well, or the method for FF to save your sessions is not functioning or your FF profile folder is not accesiable.

I suppose the first step is to invoke FF in safe mode. Then use it for a while and see if it records/restores your session.

Go to FF Menu > Help > Troubleshoot mode

Nextly, if the above didnt help, then maybe toggling the profiles from the current one you have to a blank one might prove helpful. While under a clean/blank profile, see if it will preserve/restore a session.

If it does not, then this is a clue. But if it does, then this is another clue.

To switch back and forth profiles, launch the FF profile manager via Windows Run (or search) > FireFox.exe -p