To me it sounds as if the impeller is damaged inside the pump. Alot of spa pumps use plastic impellers and being that its as old as it is, they get brittle and if debris got into the pump, it could of broken the impeller where it connects to the motors shaft. Im basing my answer on the comment about "alot of debris"
You'll have to open the pump and check it. if its broken, you'll need an impeller, a shaft seal and a housing seal .
Here is a link to the 94 calspa manual