I was going through the dungeon trying out the new trees to begin with. While in there I ran into a weird looking rare, so I decided to capture it. After a few traps thrown and it was still up, I tried again, however I did not have the option to target the sylesti. I checked the window and saw the message saying the trap was successful, and then saw that its regeneration had healed it up some.

So I decided to attack it, see if that would get me out of the battle. I got the message saying that there is no valid pet for my pet trap. I didn't even try to use a trap, only attack. After that, the window was still in the battle, but the sylesti was no longer there. I then defended with everyone and ended turn, which got me out of the battle. Attaching pictures of after the trap was successful, and after I attacked.

Okay.

So the only bug is just that it didn't disappear from battle and then the battle didn't end when it did disappear?

You still received your pet and it was normal, right?

Yes, I got the pet, so not exiting from the battle is the only bug that I saw.

I attempted to fix this.

Let me know if you encounter it again.