Sudden font change

Ever since upgrading to 1.5, I’ve had this issue where a new line suddenly starts displaying in Helvetica font (rather than Times Regular).

AFAIK, the style hasn’t changed, only the font (though I might be missing something). I have to delete back to the previous line, including removing the last character in order to fix it (faster than calling up the Font panel).

I presume the issue is that I’m typing very quickly and some sort of key combination is being pressed, but I can’t tell what that might be. I presume the “Return” key is somehow involved, but I’m not sure–I can’t (intentionally) do anything that consistently makes it happen. FWIW, I’m on a MacBook, so the Fn key might be involved, but I have no proof of that.

See this thread here. Sounds exactly the same as what you are describing, and even as the same thread title as yours does.