Unloader, maybe?

Hi Everyone, I bought a new General Pump EZ4040G, it has the “bypass loop” which goes from the unloader back to a port in the inlet, so I plugged the inlet part, and ran the other back to the buffer tank. Tried it out this past weekend on a bank, and it worked fine most of the time, but once in a while I would hit the trigger, and it would just stay in bypass mode. The only way I could get it to switch back to coming out the gun was to block off the flow coming out of the bypass hose, with my finger. Then it would kick the flow back to coming out the gun! Any ideas?