My rescue girl is 6 and her health is fine. She's an indoor cat and has always used her litter tray, she still wees in it and all poos are in it. It's kept clean, solids scooped whenever they appear and a full clean and litter change once a week.
About 3 times in the past month she's urinated at night by the back door next to her food and water bowls. There is a catflap in the back door as the old owners put their tumble drier hose out of it but it has a cover and has not been opened since our girl came.
Why is she doing it? It's only occasionally, is it a territory thing or could a cat outside the door cause it? She's happy and currently on my lap 