Was kindly left the TV by a deceased distant relative, remote control was broken but checked TV was working ok by using app on phone to switch it on. So took the plunge & bought a new remote insert (£165), and all was well for a while.  Unfortunately after about a week now seeing horizontal lines at the bottom of the picture. Tried unplugging unit for 15 mins, made no change.  Anybody got any suggestions on what this might be or how to resolve?  Could it just be a lose ribbon cable inside or something more serious. Is there a service manual available anywhere which could help diagnosis?   Thank you.