I’m not sure if this is a bug or not. When I enter Mr. or Mrs. anything, even when it’s not a name, it automatically capitalizes. I have to go in the word and not hit enter afterward to get it to stay lowercase.
I have found the same issue. If I have a character named So-and-So Jr., every word I type after his name gets capitalized and I can’t figure out how to stop it.
You can fix this behavior by going to Edit -> Options -> Auto-Correction then under “Auto-Capitalization” untick the box that says “Fix capitalization of sentences.”