It should definitely not matter which characters are in the string but you should be able to input them, which is the issue here.
Like in the past, the erase and kill characters where # and @ so you couldn't have them in a password as it would mess the readline.

This is specified in the passwd(1) manpage for example:

Quote: Care must be taken not to include the system default erase or kill characters.
passwd will reject any password which is not suitably complex.