You are probably dealing with digital artifacting.
This is common and simply the cause of a not very good digital video
processor in addition to some input signal digital related artifacting.

The red striping is also common to low quality digital decoder
processors. This may be from the digital cable box and not the tv set,
but the digital signal processor in the tv is going to make it look
much worse.

If you have any real concerns, you need to have a home theater expert
technician that not only does installations on multiple brand digital
tv systems but is also a qualified repair technician. Then they will
be able to look at the picture and determine if it is a failure or an
artifacting problem. Anything else without actually seeing it is a
wild guess.