Original drawing as composition reference "violates user guidelines"

I am using firefly to color in each frame of an animation. I drew every frame myself, they are not from a third party. 14 out of 15 frames worked just fine; however, every time I try to generate with one particular frame being used as a composition reference (with the exact same prompt line and style reference as all the others) I get the message "Your reference image violates Firefly user guidelines and was removed." I am not sure why this particular drawing is triggering that message, any thoughts?