Dropbox desktop app stuck syncing 20 files

The Advanced Dropbox Support team helped me pin this down.

In the end, it was something to do with file paths being too long, as some other members have identified as an issue in the past. In my case specifically, there were a handful of proprietary files of a .PDX extension that were buried deep in my Dropbox. That file type is essentially a bundle of many other files and folders, and so my guess is that this was creating many layers deep of file paths, causing the issue. I'm not 100% certain of this, but I know that removing the 20 or so instances of .PDX files in my Dropbox fixed this for me!

For anyone else having similar issues on Mac OS, check your file types for anything that is a bundle type (like an .app or something), and Open Contents on those files to check the file structure in there. If it's relatively deep/complex, it might be what's causing your files to stall syncing. 

That said, I would not have been able to find this on my own, the Dropbox team called out to me what specific folder was causing the sync issues and I used Selective Sync to determine which specific file in that folder was the problem (because Selective Sync will have issues also trying to delete it from your system and it will remain). Without this advanced help, you'd have to go folder by folder doing Selective Sync to see what remains. 😅

Thanks Dropbox team !