You need to eliminate possible causes.
Potentially marginal disc? Scan it.
There are other possibilities. I'm not saying "probable".
I've had occasional discs that pixilate, then when replayed- nothing. After scanning with nothing conclusive, I put it down to dust. The thing about dust is, unlike a smudge, it moves.
If you ever get smearing without blocking, it may be partly the fault of your TV. When I compressed "Hero" with DVDRB, a few scenes on the copy had smearing, mainly reds. The original DVD had just a hint of oversaturation, but no smearing. However, this only happened on one of my TVs, to this day that TV works well. But it can't handle extremely high color saturation.
Good luck. Don't forget to tell us YOUR conclusions.