It's been years since I did the bird dog thing (springers) and by far I am no expert. We trained on sented pigeons as pups and this helped keep them respectful. Then years ago someone came up with the great idea of starting them out with a stuffed dummy that looks like a small boat bumper. We tried it and almost imediately started having problems.
It wasn't as much of an issue with the new pups but it changed the attitude of the mostly trained ones. It was like they couldn't tell the difference between the feel of a sented dummy and the feel of a sented pigeon, or didn't care. They got over it with retraining but it was a long set back for our time schedule.
I think my first question would be, have you brought in any new toys for play time and what types do you use? If you have toys and play that encourage chomping (like squeeky or stuffed toys, playing tug of war) she may have an association problem going back and forth/in and out of the chomping mode. It can happen with even older well seasoned hunters. "Well, when I chomp down on my other toys they squeek and I like that a lot!!"
If she started with a soft mouth then I would look to possible changes in the rest of her world. "We always blame
THAT TIME OF THE MONTH. I've always said the I never get PMS, but my husband gets extreemly unreasonable 4 days out of every month
Let us know what's happening with her.
Norma