JML started the next wave unselectable

During the TB battle, I followed these steps:

1. In the first wave, I used JML’s ultimate on the last remaining trooper.
2. This triggered GMY’s assist, and GMY killed the trooper during JML’s ultimate animation.
3. As a result, JML started the next wave unselectable, though still playable on his turn.
4. He had no health or protection bar, no visible buffs or debuffs, and couldn’t be targeted for assists.