My dog did roughly the same thing for months. I finally came to the conclusion she wasn't actually housebroken. She would only pee in the kitchen, but would do it at random times even after going out. She wasn't being stubborn, she just didn't get it. She knew she had peed in the kitchen before, so why not now. In front of me, also not an issue, in her head, I never went nuts over seeing pee in the kitchen.
She lost her house priviledges, and I went back to housebreaking 101. Take dog out, wait for peeing, if good, give the best treat you have. Hot dogs work well. If nothing, bring the dog back in and alternately watch like hawk, or crate. Do not let the dog out of your sight. Repeat as needed. Play outside if there is has been no peeing. Only play inside after peeing outside. Interrupt inside mistakes, take dog out immediately. Make sure the inside is completely clean to keep odors from being a stimulus.
I'd still check for an infection, but Toka was perfect for months then suddenly wasn't. She had been scheduled housebroken, meaning if I was home to take her out no problem, but if I wasn't, or didn't notice her fast enough she went in the kitchen. Though it seemed really random. She now gets ridiculous praise in the morning for going outside. The first outing is bathroom only. Then we go for a hike, and only then she gets to play in the yard until I have to go to work. It's been about 3 months since she peed in the house.
--Mia