House Trained Dog Peeing on Carpet?

My dog is a Chi rescue. She came not trained at 10 months. I trained her to go via a dog door to backyard an urinate. Also before going in her crate at night she's been trained to urinate several times on command using a treat. She has been fine until 2 weeks ago when she has begun maybe every other day urinating on the rug.

I took her to the vet and she has no physical problems. Nothing in her environment has changed. I'm perplexed. When I'm not home she's kept in the family room. There are no carpets and it's where the doggie dog is located. She never has a problem in there. She goes out and I see her urinate then comes back in. When I might step out of the living room for a moment she's urinated. I use an enzyme cleaner. I've also used vinegar and sprayed the carpet. For over a year she did not do this; it has just started. What's going on?