GE Spacemaker spin cycle problems

I just inherited a “new” old washing machine from the upstairs neighbour. It worked great at first, but I am starting to have problems with the spin cycle.

When I put it on spin the agitator twists up all the clothes so that they are wrapped around the agitator or else bunched up on one side. Then the drum starts turning, and, of course, it is imbalanced, so it stops spinning and gives an imbalance signal. It’s a top load washing machine. Any ideas?

The levelling locks described in the owners manual are not there.

The problem seems to be that the agitator is spinning during the spin cycle, but the drum is not.

I just had a thought while I was searching some how to articles. I have been washing some things that had a lot of dog fur in them recently. Perhaps the tube that goes to the water level switch has some gunk in it. That should be an easy fix since I could blow out the gunk. Does that sound like it could be the problem? Can you tell me how to get to it?