Things like this are usually hard to figure out... Brina once started doing this every time i gave her a treat. She took the treat than immediately backed away with fear like i'm about to beat the hell out of her. It progressed so far that she almost stopped taking treats from me, or she would run up, take the treat quickly, then back away. I couldn't figure it out, untill one day Jaka did exactly the same. Then i started thinking that it has to be my fault if both dogs are doing it... And it sure was, it was my long nails, every time they took the treat, my nails would stab them in their gums. That was painful, especially for Brina, because she has no front teeth. I wasn't quite used to having longer nails since i've been biting them almost all of my life so it took me time to figure out what was wrong
Take a step by step analysis of the situation, take a look into his mouth, Jaka for example doesn't like tough tugs because they somehow hurt his teeth, if we use them and he gets hurt, his reaction is the same as Dakota's.