Harmy if you are going to be re-rendering the video to fix the subtitle, can you also check the encoding bitrate of the video. I’m noticing some compression looking artifacts going on particularly in dark areas. For example check the rebel briefing chapter with some of the shadowed characters in the background. I’ve only looked at the UHD version, so not sure if it also affects the HD version. It could also be because I’m on a terrible computer monitor right now with bad black levels, so its possible when I view it on a proper TV later it won’t be noticeable.
That being said without watching it fully yet, I think this is probably the definitive version of ROTJ at the moment!
I’ve found that 10-bit encoding works wonders for dark area artifacts and banding.