Edits to post randomly make parts of post disappear

I am dealing with a very frustrating issue…

I am creating a site in WordPress as I have done many times before. However, for some reason, this site is very “buggy.”

My site only needs one post (for the homepage — it’s a sales page). However, seemingly at random, when I make some edits (it could be adding some content, simply deleting a sentence, trying to add a photo, etc) … when I resave the post, it deletes major sections of my post.

I may have 10 paragraphs and then I make a tiny edit and when I resave, I only have like 3 paragraphs.

It’s very frustrating… then I have to go back and restore an earlier version of the post and start over.

I’ve tried to troubleshoot this, but I can’t seem to find any consistent reason why it’s doing this. I don’t have any crazy plugins that would disrupt it. And it seems to happen with any theme I apply (even the default one).

Any ideas?

Thanks in advance for your time…