do you get this message directly at the first stage when editing the "Application Info" or at a later stage?
I don't know which text field it means with that, but basically it doesn't like any special characters at all:
e. g. you are not allowed to use something like brackets or exclamation marks inside description. Also "&" is not allowed.
No idea what's the reason for that, but this was quite bothersome for me, too.
There is an open ticket related to this constraint. The existing thread is here: