I did notice when skipping around there’s blocky transitions from the two points I’m skipping which I think is entirely different from the blocks you are talking about, but nothing was blocky when it was just playing, just some level of grain which I assume remains in the MKV? I think both of those images are distinctly different and anyone could notice, even when not zoomed in, and when zoomed in it becomes a lot more apparent.

After taking some snapshots of my AVCHD, there’s grain for sure (not sure if that’s present in MKV) and I think one slightly offset line in one scene but idk if that’s me imagining it. But no blockyness like what was in that image.

I just wondered if the grain level was the same in MKV, that was the thing I was wondering around mainly.