Glock 42 trigger not resetting

I checked out 4 Glock 42s at my local dealer. Three of them would not reset their triggers dry firing the gun. They would all reset if the trigger was held back. We disassembled them, and it appeared to be in the trigger housing. When you pushed the disconnector in, the trigger bar would pop up. However, it didn't pop all the way up. It could be lifted up higher. Any thoughts?

Glock 42 trigger not resetting