I ran into a touch of the same trouble with my OM Vaqs. The usual cause is the base pin isn't pushing back on the transfer bar like it should. There are two possible reasons for that to be happening.
First, (the one I was having trouble with) is that the base pin is getting backed out a touch. Wolff gunsprings makes a stronger base pin latch spring that will help. The other way to address that one is switch out your base pins to Belt Mountain pins. The springs are cheap, so you may want to start there. The other thing you can do to help eliminate that issue is double check your base pins at the loading table before the stage each time. That is now part of my loading ritual. I press the base pin in firmly to make sure that it is all the way seated.
The second possible cause is the pin on the end of the base pin or the spot it is supposed to pass through being dirty. Make sure that the pin on the end of the base pin moves freely when you have the gun down for cleaning. If not, make sure you lube it. If it moves freely, make sure that the pass through hole ('scuse my lack of technical terminology) is cleaned up well so that it isn't inhibiting the pin's movement.
Hope this is some help to you!
Jack Lee