Problem with wrong cue list being asserted

I had channels recorded into Cue 9/1 at nonzero levels. Cues 9/1 and 2/1 were active. All lists are HTP. We broke for lunch. I updated all manual levels, I slid down the grandmaster, and I powered down the console and restarted it. When we came back from lunch, I slid up the grandmaster and according to the fader wing, Cues 9/1 and 2/1 are still active. The gaffer noticed that some lights that were on before lunch weren't on. I did About&Cue and those channels were getting 0 values from Cue 2/1. So apparently Cue 2/1 somehow got asserted. I did Go To Cue 9/1 and the lights came back on.

Anyone know what happened? Is this a bug?