@BeaverSquire
Yes, I was using it with Battle Fever+ and Omnidirectional Barrage+. It's possible that it happened as a result of Omnidirectional Barrage+ triggering actions that conflicted with the Combat Role Assignment script. I was noticing it when I had out Marisa, Kasen, The Freeloading Fairies, plus something summoned from Friend of a Friend, so it would probably be related to one of those three but theoretically could be, like, one of the Yukaris or Suika.

@Ada Basilisk
I was unable to replicate this bug. I've played combat role assignment with 9 copies of a red/white teammate summoned in hand and had no issues with it resolving. If the run is still in your history, could you check if you had any abilities that might've interacted with Team Up effects? An unexpected interaction with those might've been the reason for the bug.

Pretty cool ideas! I like how it plays. However, it seems to have a few bugs. Most aren't bad, but it seems like if Combat Role Assignment gets played with 4+ red/white teammates, it will stop trying to activate again and just stay on the screen, blocking the view of enemy status and the end turn bar. The game is in a playable state like this, but the card remains in limbo and never gets put into discard or shuffled back in until the fight is over, so the deck i built to use it with Team Up synergy abilities just stopped working entirely partway thru the last boss fight.

honestly the fact that people think of teammates as being green is a bit weird even with Cirno in mind,
because even just looking at the Cirno-exclusive teammates, she has more blue teammates (Letty, Kasumi, Clownpiece (though in her case she's also red and black), and the second version of Daiyousei) than green teammates (only the first Daiyousei, Lily White, and Eternity Larva), and that's before even getting to the fact that she has at least 1 teammate for every colour. she even has blue, black, and white cards that support the mechanic.