Howdy, welcome to the forum! As you might have already figured out, this is a great community full of people who love to help.
If possible, post the macro itself so we can take a look at it and see what might be going wrong. As one of the moderators likes to say, "If we're not testing we're guessing, and guessing often wastes people's valuable time". 
If you need help on how to post the macro, just let us know and we can walk you through it.
If you haven’t had the opportunity to read this tutorial, I highly recommend it. It will help you get the most help for your question.
Tip: How Do I Get The Best Answer in the Shortest Time?
On another note however, I have noticed that Messages also has a weird issue with Typinator expansions that are not present in other apps. When using RegEx to expand text it creates an extra space behind the expanded text. This might be simply an error with my RegEx formular however. So being able to see your macro would help a lot.
Also, any reason in particular you're using such an old version of KM? 
-Chris