While watching live tv if I pause or rewind the picture becomes pixelated and unwatchable

What’s the receiver model? Does this occur on specific channels or all channels? I know you may not want to hear this but those symptoms often mean a bad or failing hard drive. But, just to be sure, you can try a red button reset to see if that eases the issue. (Side by the access card for HR54 series or front where it says ‘PUSH’)