Sorry, should have clarified, I got progress back on other mods/campaigns where I'd lost progress as well, but were not crashing when trying to open the related campaigns in the mainhall. I was still getting the same crash/lack of progress with copying over the old BP save files I said I found (and I only did it with copies, not the files themselves,) I finally did delete the BP save files (.csg) related to the affected pilot, and that let me get back into action.
And the update I'm referring to, is where the pilot save system was upgraded by the SCP folks from the older, clunky, wonky, lop-sided, original way, that would bug out if you tried to run several mods via the same pilot file to a newer, sleeker, more stable, etc. that was supposed to allow us to only have to make 1 pilot, rather than working to keep up with which pilot was for what mod. I want to say that it was 3.6.15 or thereabouts, I know that it was after 3.6.10, and I think that it was post-3.6.12, but I cannot for the life of me remember exactly which update it was.