Hey Ron,
I just went through all this last fall on a beautiful Catalyst TL I adopted last fall. Sears was out numerous times trying to fix this machine, and for whatever reason, the main control board was overlooked repeatedly. Assuming that the transmission, pump, and motor components are in working condition (in my case they were and probably your case they might be), pop the end caps off the console and roll it to the rear of the machine. There is a connector P7 on the main board. On my machine, there was a problem with pin #2 on that connector. This is a white/violet wire on the harness side. Loosen the board up, and look on the back side of the board facing the touch pad and see if there isn't any signs of nuclear meltdown. In my case, it was a disaster on that pin #2. All the wiring and other components ok. I have been told that these machines are very prone to power surge/starvation damage. Surge from too much voltage (lightning strikes etc.) or starvation (overloaded circuits).
It might actually be possible that the tech sheet is still behind the console that can help you through a series of tests to determine which way you need to go. Follow the motor test sequence carefully if the sheets are there. If not, I'll get mine out and walk you through it, it's not that tough. Also, the sheets describe agitation/spin tests at various speeds. This is another area to pay attention to. In my machines case, it lost HI speed motor in agitate and spin. Otherwise everything was fine.
If you want to try troubleshooting this thing let me know. I could sit here for half an hour giving you ideas, but I can tell you it was a bit of a learning experience repairing this thing. I thought I knew everything when I started on this one, and trust me, no one does. I was alot smarter when I was done and now I have a beautiful machine to show for it. I'm curious to know if it was the motor start module they replaced, or the main board. Hard to tell which one I guess without the paperwork. But it would seem to me that somebody is replacing parts repeatedly for no reason and missing the root cause here.
Anyway, let me know what, if anything you would like to do. I am sure we can find out what the root problem is, it's just a factor of can we find parts to make a repair.
Walt