No offense intended. I’m not in the position to judge anything. A revision could very well turn out it’s good as it is.
I just encountered the same issue with Dorico Pro 6.x.
I’ve been working on the file with no issues (of this type) for the past week, and now I can’t save edits!
It is a jazz ensemble document, and I used the Dorico “setup” process with no problems previously.
One more edit: solved the problem by locating the file in Dorico Projects folder and double-click to open. Weird issue, though.