Thanks for sharing… I see the problem, still working on a fix.
The problem is that in your file you have many non-project items at top level (0 tab indentation) indentation mixed in with your top level projects. I think you wouldn’t see problem if all your top level items were projects. With that said TaskPaper “should” be able to handle your case, and I would have thought it already did, but apparently it doesn’t… I’ll try to get a fix out soon.
For example this should reproduce the problem:
And then try to drag
a: to after
c: and you will see that it instead gets inserted before
c:. Anyway thanks for the report and I’ve deleted your file.