There are some characters you can’t use like that…that is a double-byte character and although in theory you should be able to use any character, this type of character causes problems apparently. I’m just learning about this myself.
You can use arrow symbols if they have an HTML Entity representation (as opposed to an HTML code representation) those seem to work…for example:
https://www.toptal.com/designers/htmlarrows/
You can copy and paste in the character and it works fine.
I need to take a closer look at this to figure out how to fix the problem for real.