IOS 14 bugs or IPad Air 4 gen bugs

Yes I purchased a iPad air 4th gen from amazon around their release date last year, works total fine can do notes for school heat it up with work music or YouTube no issues. But if I facetime for longer then a hour it triggers purple lines on the screen that gradually travel a reboot and leaving it over night fixes issues in till another ft. Never been dropped or gotten wet never been outta beetle case. Is this a ios14 know issues or a air one?