Hi @Epearson928
Welcome to the Sonos Community!
The diagnostics show Alexa being interested in something at that time. As both your microphones are disabled, I think this must be an alarm or similar set in the Alexa app, which will need to be resolved in that app.
Another possibility (especially if your microphones were not intended to be disabled) is that you have a cat, and that that cat has a tail. If a furry limb is brushed across the touch-sensitive buttons on the top of your speakers, you could well hear a bong at some point. This would only explain erratic bonging, however, and not a regularly repeating bong. It’s more likely to be an Alexa alarm, I think - especially if it’s always at midnight exactly.
I hope this helps.