There’s nearly always a reason!

maltingsaudio

saturday night was a multi bill multi genre show with fast changeovers. As usual I put my Palmer stereo Di on the front as it’s capable of accepting jack phono and mini jack inputs. So third band came on with fiddle used for the whole set and acoustic for one song. Having checked them both befor on separate outputs from the Di when it came to the song with the fiddle and acoustic playing the signal from the acoustic disappeared from its channel on the desk but appeared in the mix loud and clear. I had a meltdown on the desk as couldn’t figure out what was going on, investigation afterwards revealed that the Di has a summed mono switch which had somehow got pushed in! 
I expect this happened when he unplugged his acoustic just befor the song to plug it into his tuner, then plugged it back in
Everyday is a school day!