All I did was use the American Typewriter typeface

Guys, I thought it'd be a good idea to type out a Word document for a passion project in the font "American Typewriter." Well, I moved the document from a Mac to a Windows, and the document started acting funny. I was just typing the word "developed," but the document kept immediately undoing the second e, so I thought "Okay, it's time to get rid of the font."

I tried using the "remove formatting" button and saving it as "plain text," but the document still acts funny. I kept wondering why I couldn't get the document formatted correctly with the font gone, but then I realized the font changed the is to some sort of weirdly formatted... something or other? I've never heard of a common typeface doing this. I thought typefaces were just formatting placed over the ASCII/Unicode characters. I can't find info about this because Google keeps trying to pull up downloads for the font. Is it possible the font changed every user-inputted i to a special character?

I'm kind of freaking out because the document is important to me, and no matter how many times I copy and paste the text or re-save the file, I can't get rid of the weird formatting. Was the Word file corrupted when I uploaded the "Word for Mac" file to Google Drive and then downloaded it to my Windows? Is there a clue? Someone, please tell me what's going on.

EDIT: I discovered that the upper case Is where lower case is should be didn't happen until I moved the document, so I guess it's partially a Mac-to-Windows thing.