I've just managed to fix a really weird bug after around 90 mins of testing (also I'm posting in case anyone else gets the same problem).

I noticed that once I drew a bow when in an interior area, I'd be unable to move for a random amount of time, as in sometimes it'd freeze for a second, other times I'd just be stuck there. Not very good for sneaking around corners. It appeared on the later saves, but not earlier ones, though I've kept the same mod configuration for the whole playthrough.

I only noticed it today, after reinstalling NMM, but restoring some old versions of various files did nothing. I eventually tried deleting my preferences, and it kinda fixed the problem. Eventually I narrowed it down to this line: "iMultiSample=2". Changing 2 to 8 stopped freezing my movement.

Somehow the antialiasing setting was causing my character to stand/crouch still, I don't suppose anyone knows why it was happening?