Well, for starters, I'm not seeing the problem on my system. I'm running Mac OS 10.11.4 and Motion 5.2.3.
Can you re-confirm your OS (Motion doesn't run on iOS) and specific Motion version (5.2, 5.2.1, etc).
Additionally, it's hard to tell, is your text 2D or 3D? It looks like it has some filtering or effect? Does this happen with plain 2D text (no outline or other effects)? Again, can you be more specific about the text setup? Details, no matter how small are important. For now, you could start by verifying your fonts. Open "Font Book" in your Application folder. Select All Fonts from the sidebar. From the File menu, select Validate Fonts (you can do a single selected font too.) Verify that there is not problem with the installed font. Otherwise you'll have to provide more about the way you created the text effect.