YES! I'm having very similar symptoms since an (involuntary) update a month or so ago. (I notice the OP is from 2016, so apparently this problem is not version-specific.) I'm now at version 8.0 on a Motorola Razr M. Since the update, if I type a word (in a grocery list, for example), then hit return, as soon as I start to type a new word on the next line, it deletes the line above and starts typing my new word. Often, it leaves the first letter of the old, mostly deleted word. It's a total mess. If I try to backspace, sometimes it works, but often it duplicates pieces of the word I'm trying to backspace into. I have to fake it out by typing my two words together with no space, then move the cursor between the two words, THEN hit the return key, and I'll get what I want. This is no way to have to type!
People on this forum talk about reverting to the previous version. How is that done? I think that might solve it.