This is at a 6-max table that just broke, only the two of us left. Villain is a reg playing 25/23/14 over 450 hands, don't have any specific reads on him (guess I need to be taking better notes). I open JJ, he 3bets, I 4bet to get it in, he flats. Already not sure what range to put him on as people differ a good amount in what hands they flat 4bets with. Maybe slow-played AA/KK, some broadway hands, some suited connectors. Flop he donks and I raise to get it in again, again he flats. Now I'm really confused. It's starting to feel a lot like AA, but maybe 99-66 or something like 65s? On turn I was pretty lost and checked back. By the river, I talked myself into believing this was some sort of awkward value line and folded. Then again, I've noticed 6max regs tend to spaz when they get in a heads up setting. Do you call river? Jam turn?