Might be time for a new set of locks? Sounds like an internal bit has broken. They aren't hard to change out.

Of if they are a good quality mortise type lock or a hi end cylinder lock they just may need servicing and or lubrication with graphite.

Probably they would benefit from some lube. The one you used most often quit first. When you switched them, the other one was not far behind. Locks have moving parts and need to be lubricated. Look for some lock lube in a spray can with a little straw taped to the side of the can for shooting it into the lock. They will be so smooth after that, that you'll wonder why you never did it before. Or, they will still be sticky and new locks are in order.

Thanks all! Looks like it is time to spring for some new locks :)