Why do I keep getting Mode Shift Circuit error codes?

After running a load or two, the washer quits working and gives the 4 flash Mode Shift Circuit Fail code. I re-set the washer and it runs fine until another 4 flash code comes up, and I re-set it again. What's up? GE model WBSR3140G0WW. Two loads of clothes run fine. Then on the third the washer will not do the final spin. The Fault LED blinks four times in sequence. According to the fault code chart, this is "Mode Shift Circuit Fail". I perform the re-set procedure and it will run fine for another two loads. I don't see anything else wrong.