Some very old tabs from some windows turned into "New Tab" and lost their content while others are fine

Good evening. I leave my windows and tabs open and turn off my computer by clicking the shut down button on Windows 10. The next day I open Firefox and all my windows and tabs come back with no problem. I've been doing this for a few years and I gathered dozens of Firefox windows and hundreds of tabs. Now that I'm finally ready to organize what I've been putting off I noticed that most of these old tabs disappeared in a very weird way. When I open Firefox it still opens all windows from these past years but it loads most older windows with a single tab and these single tabs are all in the New Tab state. I'm sure that these used to be unique tabs with content in them and not New Tabs and I'm also sure that these windows had many tabs each and not just one. The tabs have the name "New Tab" on the tabs bar and they're gray and empty, which is what I set all my new tabs to be, so they're regular New Tabs aside from the being lighter gray than a true new tab page. Refreshing and F5 have no effect. I can't go back a page or forward because the arrows are grayed out. I can't figure out what these tabs used to be by browsing my history because they've been added to the pile sporadically over the years and are mixed with other web pages, most of which I don't want to open again, so searching for all of them would be too hard. Tab groups that only contained these "New Tab'd" tabs have also disappeared and can't be found on the tab groups list menu. If I go to "View recent browsing across windows and devices" and then "Open tabs" these tabs are shown as "New Tab" and if I click the three dots menu and select "Copy link" it copies "about:blank". Though this is not the most specific fix, I went to Firefox>Profiles>(Profile name)>sessionstore-backups and (after making a backup) deleted all files from there except for the one with the oldest modified date. I did this with Firefox closed and then I opened it and a few of my old "New Tab" windows became real windows again with multiple tabs inside. Curiously, the recovered windows and tabs were not the most recent ones that were affected by this problem and most windows are still lost in the New Tab state. I think Firefox has been failing to restore older parts of my session but only kind of because it still recognizes the total number of windows I had but then it opens many of them with no content (a single New Tab) and no memory (arrows grayed out). I've always updated Firefox throughout the years and I don't know when the problem started happening, it might have started months ago and I just didn't notice because I stored the tabs and didn't look at them again until now. I also noticed that windows that were in my most recent and most used desktop instance were fine while windows in my "storage" desktops were more likely to get "new tabbed", but maybe it's unrelated to desktop environments and only related to how recent windows are and most of my newer windows are in the newest desktop, but I can't know for sure because sometimes some windows move around desktops after a PC shutdown so it's impossible to know if windows are sorted between desktops 100% by age, I think it's a Windows 10 problem. Also there have been some forceful PC shutdowns over the months due to power outages, and I have removed my drive and used a different drive with a different OS a few times, always switching with the PC turned off. Does anyone know how to get Firefox to remember my full session and find out what these fake new tabs used to be? If not, is there a way I can restore my session to a state that it was previously like months ago? I would need something more powerful than the sessionstore-backups folder because it only helps me roll back a few weeks. I have backups from the bookmarks windows (ctrl+shift+O) but I don't think they save active open tabs. Just curious, do they save browser history? It wouldn't help me in this case as I mentioned before but it's good to know. Thanks for your help and sorry if it's overexplained.