For added safety, make your withdrawals during business hours.
If something goes wrong, at least you can go in the bank and try to resolve the problem.
Also, try to get the info right on the first try.
It seems that when people retry several times, the ATM's often gobble up their cards.
If you have trouble with the Banco Popular ATM, there are 6 or 7 others in Sosua, all in walking distance of Casa Marina.