Sync problem. – Papers 3 - Reference Manager Review

This version(3.4.7) has a problem to download my PDFs in a synced Dropbox library. It redirects me to some PDF urls such as IEEE Xplore even I have the right file. This is very disappointing me. Except this crucial problem, this app always have problems to sync files between multiple devices. It is TOO slow and sometimes is not completed at right time.
Review by J2J@J22jjcc on Papers 3 - Reference Manager.