Teamfight Tactics Bug - Enemy Unit on my board

During a ranked match, a Darius enemy unit appeared on my bench after I had sold two of my own Darius units. I could not sell this enemy Darius unit that remained on my bench. I could upgrade the unit when I purchased additional Darius units. However, when I put this unit it in play, it started attacking me. At the end of the round, the unit reappeared on my bench.