I have rested for over 24 hours, have used a cure shrine, have removed entire inventory (Except keys/Golden Claw) and it had no effect whatsoever on the problem. The base skill level is 51, several increases while inside. The noticed level after penalty is 15. Whatever it is, I suspect the problem trigger is setting the skill to that level specifically.
Going back through my saves, I noticed that the problem was present before the dragon wall in Bleak Barrow prior to triggering it but not present before approaching the entrance area outside. Upon approach, my character was level 18, 19 soon upon entry. I was using the Spectral Assassin summon for most of the duration of my adventure inside. No idea whatsoever how I picked up that bugged penalty, but will post more specific information should I happen across it after reloading my game. (Lucky for me I actually have archived saves and noticed before I got more than a couple hours on from there.
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