Random scenes deleted from project

I went to work in Scrivener as usual but as opened my project I discovered that roughly 10% of my work was gone. Random (non-sequential and not the most recent) scenes were simply empty. Luckily, I email myself the compile file at the end of each day so I have the words, but wtf? I’ve loved and not had problems with Scrivener but this is nearly enough to make me walk away. I’m going to have to go through the whole thing line by line to make sure other bits didn’t also magically disappear.

I’m on an iMac running Catalina and using version 3.1.5

Where is your project saved?

In Documents.