Good luck and I 'm glad your dog will see the vet tomorrow. Chris
I can not evaluate what is happening since I can not see anything live.
My my opinion is that you are searching for a suggestion that will give you the fix. My concern is that you can create confusion, frustration and generally degrade good training progress by seeking quick answers from random contributors that have not seen what's happening.
Nothing is is lost by waiting til the doc evaluates health.
Who knows? There is a chance that your dog tried hard to do the right thing and somehow hurt his mouth. Maybe he hammered down on a rock or root and it hurt him and confused him. If that's the case, you will need to work through it. That is only one of an endless number do possibilities though.
Good luck. Be fair, be patient, be reasonable.
You only get one chance to do it right the first time.