file-contents-sorter doesn't use consistent order with --ignore-case option

[alexdewar]

I'm trying to use file-contents-sorter to keep a dictionary file sorted, ignoring case. The hook runs fine and updates the file, but when I attempt to commit the changes, it resorts the file again, moving around some entries which differ only in case. If I try to commit those changes, the process repeats.

[asottile]

works fine for me? please show an actual reproduction