Triggering event missing/not logged--?possible bug

I have a motion sensor which is listed as the trigger for 13 rules. However, today one rule didn't get triggered when it should have.

While investigating, I noticed something odd. Here are the events listed for the sensor at another time, when things worked correctly, showing the 13 rules. The one in question is the last one, which I have highlighted--which notably gets listed even if the required expression is false:

However, this instance shows only 12 rules, with that last one missing (incidentally, the required expression was true). This is when it failed to get triggered:

Here is the log from the rule, showing that the motion trigger which per the device event list happened at 18:24:15.754, is missing. It does show the subsequent triggering at 18:29:21.219:

Here is the rule--sorry, it's a bit involved, but I think the only thing that matters is the triggers:


Does this seem like a bug?

More info:

I find that this is somewhat reproducible, in that it happens at other times, but I'm not sure why. I must be missing something here:

The rule is triggered appropriately:

The rule is not triggered: