I am currently working on a 2007 36M Concord mounted on a Mac. The operator complains of intermittent Accumulator pressure drop off. This only occurs on long pours when the volume control knob is adjusted. When the accumulator pressure drops off the material cylinders run at full speed. The problem can usually be corrected once the pump is turned off by the remote and turned back on. The accumulator has had a new bladder installed and been recharged. The pressure relief valve for this system has been verified that it is adjusted correctly and been operated with a new relief and had the same issue. I'm just curious if I'm dealing with hydraulic or an electrical issue causing the accumulator pressure to dump off. Any help here would be greatly appreciated. 

Probably compensator on accum pump needs replaced - or the entire pump itself.  Concord takes accum circuit oil to control big pump volume.  Lose accum oil (and therefore pressure), then pumps go to full volume, and obviously accum prsssure goes to zero.  Failing compensators tend to operate better at lower rpms (hence hitting estop and clearing it fixes problem).