Hi Addie, according to my experience when your dog is in a thinking state, it happens that one of his ear is up and other is down. He might be planning for some thing excited. It also means that he is seeking your attention or wants you to give him his favorite treat.

What I think is that if you own a young dog, it may be a sign that his ear or pinna are under development.

Also if you look closely, if the dog ear is reddish it is sign that he has developed some sort of allergy or infection in the ear.

According to my experience when dog has one ear up and one down, it means that he is not getting proper diet he needs. I suggest that you should add liquid vitamins in dog food. I hope it will solve the issue and he will start behaving normally again.