I didn’t know! I read a lot about this same problem through FTP (the main culprit, I guess, would be on the server side for lack of support) but I missed, then, the references about the same issue on Dropbox.
Has CloudSync the same issue?
Anyway, I was doing a tough test by coping thousands of files (with FreeFileSync), and my PC, after long time, became extremely (truly very) slow. As I could see, there was very little free memory, but I don’t think that was the only issue. There was thousands of files still in the queue to be uploaded and I had to restart my PC. When restarted, I connected the Dropbox NetDrive drive. It took a while to connect but everything that was in queue to be uploaded to Dropbox cloud disappeared.
In fact, trying to recover for the PC extremely bogged down situation, I didn’t do just a restart. Before, I disconnected the Netdrive Dropbox drive and next, a connect (as I know of, there is no kind of pause command to stop the upload or any transfer for that matter. The pause command could be a good thing to have if a heavy upload/transfer is going on, when that bandwidth is needed for something else). As the reconnect was taking a long time (I mean, really very long time) and the system was quite bogged down, I had to initiate the (extremely slow) shutdown. When the PC came up and I started the NetDrive Dropbox drive, there were no files left in the queue to upload, thousands of files have disappeared.