I initially replaced the main circuit board. That was complicated and didn't help. Then I read that the "filter" was an **electrical** filter board and often caused this problem. I did a few tests that suggested it was indeed the problem and ordered a replacement board. It was a quick (15min) fix once I had the part, much easier than replacing the main circuit board had been. It was helpful to use a LARGE needle nose pliers or slip jaw wrench to pull out the tabbed connectors. It's still a little dicey (particularly on the main circuit board). Suggestions are welcome.