Sounds like a stuck sw even if its fixed itself. As I have posted many times there is an MB bulletin to remove clear bellows of sw as they make them stick or stop them working properly.
Later fix was/is to replace switches completely.
I just bit the bullet and replaced 4 switches at $20/each. Actually have one more to go in but the problem was so intermittent that I decided to just swap the four instead of try and troubleshoot it. For $80 total I figured it was worth it.
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