It sounds like a game bug to me. Since the moderators read these threads, they should be sending this to their programmers to debug (fix) in the next release.
I have a polymorph glitch too.When ever i use mostly any polymorph on the last turn and the enemies die before i use it.Then the battle ends i still have the polymorphs health.Like if i transform into a treant on the last turn i have 3000 health when i have around 2800 something.If i port or quit the game or enter a battle it goes back too normal though.