I had a similar problem on the open center single spool valve on my 28 ton Huskee. I took the valve apart, cleaned it thoroughly, there was some old grease, whatever else, and when you put it in return, the detent would not release like it should, would stick and almost stall the motor. This took care of it, I lubed it with white lithium grease, no trouble since. On this one, there is apparently a factory specification for the detent to release, there was more to it, as far as making an adjustment, something to be careful of. In my case I figured it was adjusted right per the mfr, just needed a good cleaning, condensation, old grease, a little rust, likely from the previous owner not leaving it under cover. Works flawlessly now.