I encountered a question in a close-review queue (this may be significant?) and edited it to bring it back on topic. While I was editing it, the notification bar indicate it had been concurrently edited.
When I completed my edit, I tried to save the edit, but the system rejected it. I was surprised that someone had done a more thorough edit, but I copied/pasted my changes in to a new edit window, and saved it that way.
I checked the revision history..... and found that the "competing" edit was trivial: See revision history here - note the competing edit removed "using Linq" from the title.....
Why was my edit not approved? Why is it not "more thorough"?