I had been working on a post, and had been regularly saving by clicking on the "save" button while in distraction-free mode. I left distraction-free mode, and then clicked "save draft", and my entire post, except for the title, disappeared. The draft remained, but all of the content was gone. I went back to look at my revisions. The most recent couple of revisions - 3 or 4 - were all blank as well. But before that the content had saved properly. I resumed working on the post from that earlier successful saved draft, but then it happened again several hours later, exactly the same.
I made a draft without any problems a little over a month ago.
I am using Firefox as my browser. After it happened for the first time, I disabled all of my add-ons and extensions, though I didn't have any related to WordPress. I deleted my cookies and cache. This didn't make any difference, since it happened again.
I'm not sure what to do or what's wrong.
The only time I've ever had a problem before was when I made a huge post several years ago with a ton of large GIFs and HQ images. The post I'm working on right now contains quite a few images but not nearly as many as that other post, and I'm still in the middle of it, not towards the end.
I'm not very savvy, I don't have any WordPress plug-ins and I haven't messed around with anything except simple things like changing my header and arranging my widgets.