I have encountered this problem on Jellyfin before. It works like a dream, but there are some very strange circumstances that can cause the database to become locked and then just not work until I restart the docker container. If I check the logs it just says stuff about the database being locked. It happens quite rarely and seems to be when we fidget in the menus on the smart TV like starting to watch a show to realize it's the wrong episode as you click the button, then spam the back button, etc.