(adj) When a person, group, or other collective makes a decision(s) or commit action(s) that present problems for them and/or others which would tend to make an unbiased third party observer believe the perpetrator(s) is(are) mentally unstable.
"Joann's tendency to throw up after she eats is very problemental
"Stevo has been so problemental
lately; his irrational behaviors are quite disconcerting."
"The NRA's defense of guns after the Sandy Hawk Massacre is very problemental