I have the same pumps. Yes I believe the balanced relief valve is faulty. It's not reacting to the change in volume properly. It needs to stop bypassing when the trigger is pulled or the overall pressure will reduce. Depending on what brand you have, some can be rebuilt on the cheap. Ive had pretty good results rebuilding them.
Do you have a weep system? Or what type of pressure valve, is it like this one?
Hmmm yeah I've had that happen before with the cavitation fromIf the inlet check valve is not opening fully the pump will sound fine until the trigger is pulled, then it will clatter loudly from the cavitation.