I have a custom property that had one letter that was mis-typed in lower case [Screen Normal y] where the "y" should have been Upper Case. This has no affect on function. But it does take a toll on my sanity. Unfortunately, this oversight was not noticed until it had propagated through a number of files.
Simply enough, I just changed it to upper case when I next edited the file.
But... it comes back as lower case. Edit, CTRL-Q rebuild, save to your heart's content and the "y" will be lower case the next time you open custom properties.
For months I lived with it and accepted it as a "SolidWorksism". More pressing business called.
Today it was poking me in the eye once again when a new but simple approach hit me - and it worked.
I simply changed the name of the custom property to something COMPLETELY different - call it "toast" or "Ni!". Save the file. Reopen the custom properties dialog and rename it back to what it should be. The extra "shell game" maneuvering convinced SW to let go and allow the change.