Lower PSI usually means a suction side restriction or problem. Do you see air in the pump basket? If so, check the skimmer basket(s) and pump basket for any blockage. Also check your valve settings if you have any.

It could also be that there is something on the pump impeller but to find out, you would need to disassemble the pump.

Also, because of the suction problem, the pump may be overheating and shutting down. If you fix your other problem, the pump may still be ok.