I have Dropbox Sync to my ReadyNAS 2120 (running firmware 6.10.8, which I think is the latest) but it can't seem to ever finish the sync (i.e., the blue dot next to Dropbox app under Cloud tab never turns to green dot). I've been trying to do this for weeks, and I only have 750 GB of data to sync. My Netgear Router tells me I'm transferring over 250 GB a day, so it should have taken only a few days to sync rather than never being able to sync.
I downloaded the logs and there are hundreds of errors, but the most common and recent error is: Curl returned error code 18. Transferred a partial file.
It seems like the Dropbox sync is literally just spinning its wheels and trying to transferring a file, failing, restarting, failing, over and over again.
Please note that I have Dropbox sync on another ReadyNAS (same Dropbox account), that is usually turned off but I turn it on once a week to let it sync up. I don't think that would have caused interference, but maybe?
