My troop attacking my own troop

game 1,402,176.

For what it's worth now being that I am almost out of the game. I had a tank in a city and it showed it in combat status, being that it was the only one in combat status figured it was just a display issue so I sent it to another province before I went to bed, with a listed ETA of some 2 hours. When I came back on the morning its still in the city fighting. Further searching it was being attacked by my own aircraft convoy but the convoy doesn't show fighting status. Here is the proof.

http://prnt.sc/a8659k