F20 stops the machine but ONLY on large, thirsty loads like towels, flannel sheets & comforters. It occurs on these loads no matter what water temp I choose. When I unplug the machine for a few minutes then plug it back in, I hit cancel then start it again as a new load. This most always works the first time. Occasionally, I've had to repeat this to complete the load.

I've already ruled out debris in the filter. If the water inlet valve was the problem, wouldn't it be throwing the code during other loads as well?

What should I check next?