Aspect ratio changes and have to unplug and reset box

[duane1311]

I have had fios for years and never a problem until about 3 months ago. My tv is an LG 4k about 2 yrs old and  also go through a yamaha receiver. I have alway been able to watch full screen until 3 months ago I got the black bars on top and bottom. It just happens all by itself and the only way to fix it is to unplug cable box and reset it. When tv comes back on it is full screen and could be good for a week then does it all over again. Has anybody else had this issue? Thank for any suggestions