This has also happened with me... Maybe not a week, but after a few days I loose access to the webGui...
One thing I've noticed, is that this only happens if the Plex Docker is running... after a few days I loose access to the WebGui... I've tested not starting the Plex Docker, and it's running smoothly for weeks. As soon as I start the Plex Docker, a few days later I loose access to the WebGui.