I just had another example of Word doing this and thought of posting it here in case the extra detail helps.

Mostly I type into Notepad++ because I am familiar with it from working with code. I type each paragraph as one line and separate them by a blank line.

I had a page typed. I opened a new docx from the start menu, called document1. I pasted the page from NP++ into the Word page to check spelling and grammar suggestions. To my surprise it kept the formatting perfectly, which only happens about 20% of the time.

Thinking about this topic, I checked paragraph > spacing. It is set just as the template is, at 0pt, 0pt, single.

I went back to NP and typed in another paragraph and then copied the whole page again. I went back to exactly the same document1, selected all, and pasted text into it again. This time it comes out completely different. There is a huge blank space between each paragraph. I check the paragraph settings, and they are now at 0 pt 10 pt multiple, and 1.15.

No settings were changed by me between these 2 pastes, either in NP or in Word. No new document was opened in a different way.

What is going on?

sincerely baffled