I have had this issue since I bought the router several years ago. In fact, this is the issue that forced me to setup the router to reset itself weekly so it wouldn't go into this weird state, but then I also discovered that the reboot functionality doesn't always work either; however, automated reboots once a week has made this a very rare occurring thing on my end... I would recommend you do the same. I set my router to reboot every Monday at 05:00