The checksum is a numerical thumbprint for the file, to see if it’s been corrupted. Harmy posts the checksums for his files in the first posts of his project threads. You just Google around for a program that will give you the right kind of checksum (MD5, SHA-1, CRC32), and see if the value from your file matches what Harmy posted.

Subtitles that flash for one frame (only in VLC) was a bug this project had a long time ago, apparently about the time the AVCHD for Star Wars was made–it was definitely fixed by the time ESB came out. The subs are at fault, but they did work on every other player I tried, including hardware players from multiple manufacturers, MPC-HC, etc. You could also fix them by muxing in SUP files from the current project, but again you need tsMuxerGUI working to do that. And I don’t think ROTJ had any subtitles at all at the time it was released.

EDIT: Also keep in mind that in addition to not using a Mac, I don’t use the AVCHD versions either. So if you’re following this thread and I’m missing something, please feel free to chime in. I also don’t use the SRT files, so if there’s a way to get them working with the AVCHD, that may be another option.