Kenmore 417.29042991 spins but won't agitate

[Stillwater]

Got a confusing problem. Here's what I know about the Regular cycle:

Fills and drains fine, both water temperatures, but the drum doesn't rotate slowly in either direction, in any part of the cycle. It does not move at all until the final spin. 

The final spin works as normal, slowly clockwise for a few seconds, then fast clockwise for about a minute (when empty) then coasting to a stop. 

There is also no slow rotation in either direction after the final spin has come to a stop, which it used to do. 

In short, the drum and motor don't move except for the final spin. 

Here's what I know about the various parts:

The door lock seems to be fine: the "door lock" light comes on, there's no change when I push in on the door, and the solenoid isn't buzzing like it does when the door is not fully closed. 

The drain pump runs (I can feel it vibrating) appropriately, the tub drains fine, and good flow rate exits the discharge tube. 

Final buzzer works normally and sounds at the correct time. 

The motor speed controller is highly suspect except that I can hear the relays clicking on it at all the times the drum should be changing directions. The tech sheet I found inside the cabinet includes a series of diagnostic steps for "motor will not run" so I went through them even though it spins fine, and some of the steps are strange, others bizarre. For example, step 3 says to measure voltage between pins 2 & 4 of the 4-pin, and you get no voltage suspect the motor thermal cut out. I got 0 V, but it can't be the motor thermal cutoff because the motor runs fine for the final spin. Bizarrely, step 5 suggests checking voltage between pin 3 on the 9-pin plug and pin 4 of the 4-pin plug. Well there IS no pin 3 on the 9-pin plug; it's an empty hole, no wire there! I got no voltage on any combination of pins on the 4-pin plug when the cycle was beginning (but empty of both clothes and water, per the instructions on the tech sheet), which would be relevant except that the motor isn't supposed to run when there's no water in there yet. I'm thinking the tech sheet is just wrong or poorly written. 

The belt is in great shape; tight, good contact, no hot smell, all good. 

Drum suspension seems good; drum moves smoothly (but not excessively) in all directions, nicely balanced, no banging. 

Timer feels normal when turning it. 

Bottom line:

I suspect the motor speed controller and/or the timer, but which, and how to tell? There are no error-code LEDs on this machine. I suppose it could also be the motor if there are different windings for slow speeds, or something else I've never heard of. Help!! (and thanks)

[Stillwater]

Bought and installed a new timer as suggested on another forum - waste of time and money - the symptoms continue as before. 

Noticed just this morning that the wiring harness at the motor is partly melted and browned around pins 2-4, which DO have alternating voltages as expected during the tumble cycle, which suggests it's the motor that needs replaced. I'll have to replace the harness as well, but I don't know how; it's discontinued at all the parts suppliers I can find. 

Your thoughts? Could it still be the motor control board?