Dropbox has major serious problem with download manager especially IDM. The problems that I faced when downloading a large file (let's say around >3GB) are listed below :-
1) It will download only with one connection, not the usual 8-16 connections like from other sites.
2) The download speed is capped to 30Mbps while I have 100Mbps connection
3) The download will fail after reaching specific point due to timeout error and cannot be resumed.
4) Getting 403:Forbidden/409:Conflict errors when try to resume with refreshed link.
This needs to be sorted out as soon as possible.