This was it. I cleared the troop then readded the enemy and now it works fine. Dunno how that happened as I didn't mess with enemy files, but I guess it got messed up somehow lol. Thank you so much!most likely the troop of that battle has an enemy that is missing a sprite or some data.
the reason for that missing data could be an old save, it could be a deleted database entry or an incompatibility of a plugin.
This thread is being closed, due to being solved. If for some reason you would like this thread re-opened, please report this post and leave a message why. Thank you.