I've seen people lose months on this one. When we use the alt number method we have to also see if the font in that form or application has some character of interest at that location.
CHARMAP is good to know about here. But what font is being used in the app?
I have search the fora, and cannot find evidence of anyone else encountering this problem.
Admittedly, I think Unicode sucks, it was set up to handle 65000 characters, and now has a table of some 95000 many of which are compounds of existing characters.
As a "typographer", I go for the closest to correct "spelling" as possible which often includes compound characters like "