I took a look and I see that all of the active files are inside “.fcpcache” directories. They looks strangely nested, with multiple instances of the .fcpcache folder within the same hierarchy as if they are self-referencing aliases/symlinks.
For example:
/iMovie Library.imovielibrary/.fcpcache/.fcpcache/.fcpcache/.fcpcache/.fcpcache/.fcpcache/.fcpcache/.fcpcache/.fcpcache/30 going on 6/Render Files
From the diagnostic, every actively syncing path is similar, where there are multiple .fcpcache folders in a nested structure, starting with …imovielibrary/.fcpcache/
I was poking around a bit and this seems to be an issue encountered elsewhere. I don’t have an iMovie library to verify, but some reports say that the .fcpcache folders point back to their parents, in some cases, which would create an infinite loop.
I haven’t done enough research to know if removing these cache folders is an option, but I anticipate that, if you did, this issue would go away.