Yes. For ROTJ it says it’s part25 that is the issue.
I did manage to find a workaround though. Apparently, if I download ALL of the files using the individual MEGAlinks, the ISO then extracts without issue. It’s when I download them using the folder links (imported into MEGAsync), or mix and match file from the folder links and individual links, that I get the errors.
So I’m just redownloading the files individually.