The upload-server refusing to accept, or client not managing to connect at all to upload-server, so the upload goes into backoff and is retried at a later time can happen with all clients. Ocassionally the reason for failure is a "locked by process-ID", something that if you're unlucky won't clear-off until server is re-started. But, since such uploads does backoff, they won't block other uploads from trying.

The "stuck" uploads in the old v5.10.xx/v6.2.xx-clients on the other hand is really "stuck", such an upload is easily spotted, since it's the upload going at zero speed, and often at 12+ hours. A look in the log reveals the upload did start 12+ hours ago, but has never stopped again...

With default settings, 2 such stuck uploads, and your client won't upload anything at all, until manual user-intervention, or power-outage (something that can take a long time, especially if you've got UPS)...


A small car-analogy, with v6.10.xx, the "stuck" upload is just a car that has trouble, but regardless of how serious the problem is, still manages to get the car to the side of the road so other cars can move past the car having trouble.

A "permanently stuck" upload in v5.10.45 on the other hand is that the car blocks the whole road then has a problem, so until the tow-truck comes and removes the car blocking the road, no-one can use the road...