This is just another thing that he's doing - outside of the game, but still pretty stupid, it's really not hard to remember to not drop the flag - that is him acting without thinking.
It reminds me of him fumbling against Cincy (as you mention). It reminds me of him trying to jump his huge frame over people instead of bowling them over. It reminds me of him arguing with Campbell last year about being out of formation and forcing the team to call timeout (which was ridiculous).
He plays with a lot of heart, fire, and passion, and he's a big guy. I give credit to Gibbs to recognizing that's not enough and limiting his role which I really criticized at the time and wondered about. It's another lesson in how the coaches see a lot more than we do, and we should be careful with judging based on our limited perspective.