Line spacing code appears.. broken

Been running into this a lot lately. Figured this was the place to address it. Recent issue, though; happened occasionally before but now I’m having to edit (and sometimes RE-edit) my posts 80% of the time or more to make sure double spacing works.
If I hit ENTER twice, it gives me a single line down. I have to edit it and hit ENTER again to make it do double and sometimes that requires a re-edit when it just erases my line spacing entirely and pulls an entire paragraph onto the end of the one above it without even so much has a space.

If you can see my editing history, it should be sufficient to show this is indeed occurring. Just giving you a heads up, guys!

Unless of course it’s something wrong on my end, then please advise!

- Aulakauss