Hard to say much without knowing more. Some ideas:
Enable all logging for the Basic Rule in question.
Examine the output of "Logs," filtered to just this Basic Rule instance, for clues, if there are any.
Verify that "Switch A" or whatever should be triggering the rule is actually sending events--go to "Events" from its device detail page and see. (Logs should also give clues but are not the definitive source; this is.)
Try just hitting "Done" in the problematic Basic Rule to "re-initialize" things and see if it helps.
It may also help if you could post a screenshot of the basic rule you have having problems with. Equally, it may be useful to see a screenshot of the rule that is working.