Hacking join .rar to make image?

[Lexip;]

I've noticed the errors also happen if you create a .rar file using 7zip (instead of a 7z file)

Since when is 7zip able to create rar files? Are you just renaming .7z files .rar?

QUOTERAR files may be created only with commercial software WinRAR, RAR, and software that has permission from the licensor Alexander Roshal (Eugene's brother).[2]

Third-party programs that can only read (unpack) RAR files include: ...7 -Zip (multiplatform), ...