What are the signs of a dirty 4k UHD lens?

[mdhaus]

Tonight, I was watching the new Cliffhanger 4K disc and at about 15 minutes into the show, it flashed some rainbow colored video glitching in a section of the screen. I reversed the disc a bit, hit "Play" again, and it did it again.

So I popped out the disc and thoroughly wiped it. I re-inserted it and this time it played through that part OK...but then a few minutes later, I got another portion of the same thing along the bottom portion of the screen. I reversed it again a ways and this time it began stuttering and all of the audio completely dropped out.

Is it a bad disc or perhaps a dirty laser or something else instead? The reason why I wonder if its a hardware issue is that a couple weeks ago, I had the exact same thing happen on a Superman 3 UHD...and it happened at about the same time into the film - about 15 minutes in. A replacement disc solved that problem.

I've watched 3 other UHDs and a Blu-ray movie since then and they played back great...but I'm just trying to figure out if maybe the unit needs servicing. It's odd to me that taking the disc out and wiping it would make it work OK in that section, just for it to glitch out again a minute or so later, to the point that when it totally lost audio and started to REALLY glitch out, it was doing that even in a section that played OK a little bit before!

It's a Panasonic 9000 and I have an extended warranty through Best Buy. So it wouldn't cost me anything to have them clean and service it. Thoughts? Thanks!