I've done a total re-install and the problem was the same. I'll try the different drives. Cheers.

Different drives = Same problem

I'm out of suggestions for now. I think there was someone else
with the same problem here. Tried to find the thread, but couldn't.

Sorry I can't be of any more help.

Will, I see the problem but I'd like a closer look at exactly what the artifacts are compared to the original frame.

Could you try putting 2 copies of the original footage on the Premiere timeline, then dissolve between them?

That way, you can post the original frame, and a rendered frame, and I can compare in detail only where the artifacts show up.

I know this is a lot to ask, but it would really help to have those 2 identical frames to compare, with the only difference being the artifacts.