I can add a
after the ? with and without a space between with no problems when I preview.
I'd need to know the exact text entered which causes the error, probably best as a screenshot. The shortest text that causes the problem to occur consistently.
If you are using emojis from a mobile device though, they don't work correctly here and are outside the area I would try to get fixed. Only the smilies within the forum system are expected to work.