Unable to use text selection styling sometimes styles the whole text frame

I've only run across this a few times, but if I select some text, and try to style it with a superscript or color or a font, the entire text box will be styled that way. It's not grouped together or nested, and will happen across different files. If I just italicize using key commands (ie command-I) it works. And when sent to a coworker with the same setup, everything works just fine. If they resave and send back, the same issues persist.

I'm on the latest XD (47.0.22.9 x64). It seems to happen to any XD file I open or new ones I create. And just as mysteriously it'll stop, but it doesn't help me in the meantime.

Any ideas? TIA! 

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