[Ayoka]

There is an AKC rule that says "the judge will excuse a dog that attacks another dog in the ring or appears dangerous to other dogs in the ring" and I could see how a grumble may be interpreted as dangerous - even if it is ranter innocuous. however, I was not aware that a person/club COULD deny entry to their trial unless it was a limited entry/specialty club thing or a dog had ben DQ'd excused.

In my opinion a dog that means to attack/bite another dog will do so. If she grumbled but wasn't staring at other dogs and held position - she clearly didn't mean to attack.

I wonder if the grumbling is an attention getting thing which you may be inadvertantly giving her by trying to get her to stop it? Or, maybe reinforcing a good down when she grumbles is reinforcing the grubmle AND the down?

If she's only grumbling during certain exercises what about ignoring the grumbly ones and rewarding the quiet ones?