When I noticed his speed increase, his attack and defence decreased, so I think it might be a bug in encumberance. I don't expect a fix, but that would be nice, though it might just be me. In which case, has anyone else had this happen? aka unexplained negative effects on attack & defence stats, as if you were encumbered, or seen their character speed up for pretty much no reason?
Glitch typically occurs after picking up loot, and then selling it, there might be another thing affecting it, though I'm not sure.
Image proof:
speed:
-30 attack (yes I know the affected character is 70% encumbered here, but that didn't affect him at all in game.):