Hello @jwfx,
First, I would like to thank you for providing a full reproducer! That was very helpful!
I was able to pin down the issue, and it is coming from the C# Analyzer plugin.
We consider any issues with the start location and end location being same as a file level issue.
I have created a ticket in our backlog.
Unfortunately, I cannot share it with you as our backlog is private at the moment.
Have a nice day!