Edit: see my post after this one...
In your picture the "Output" module is not shown on the track strip and in the Track View Bus Pane the "Control Filter" is not set to i/o so se cannot see where the bus is outputting to.
I checked in Foxboro and you cannot set the Metronome bus to itself. This may have changed with the new track to track routing feature but still doesn't make sense for it to set itself manually.
How exactly are you changing the ouput of the Metronome Bus? I ask because AFAIK you can't without exposing those areas or using the Inspector.
Sorry to be tedious but we gotta make sure the output is indeed going to the Master.
By the way... I didn't mean to insert a "Send" module. I was referring to the main bus strip output.
Cheers.