I dont think you have a problem with either of the valves. I think the problem is one of your retract cylinders is allowing air past the O ring. The reason why its doing what its doing is that the air is getting past the O ring and coming back down the other pipe and then coming out the robart valve as this pipe is not sealed when the valve is in that possition. To check this, clip some forceps on each line in turn untill you find the offending cylinder.

Jason