Fixed it.
I went to the save folder and manually deleted both files. It seems that the game refreshed it saving function? maybe I just got unlucky the first time saving, and the save file got corrupted somehow?
I mean... it's possible. Lots of things really are possible.
For instance it's possible to accidentally shove items through physical bounds/objects... I can't imagine what might happen if an item was saved whilst inbetween boundaries - I've seen, for example, a Katana blade/curved greatsword blade, fall halfway into the workbench with the most minimal amount of it sticking out, at one point, it was entirely inside the bench, not one ounce of it was exposed....
I eventually worked it out, but what happens if its something you don't even realize exists, that spawned and fell into something it shouldn't have, and then you save/exit?
But anyway. Glad to hear it's "working" now. - Hopefully, by the sound of other recent reports, it stays working and doesn't fall back off the deep end....