Yes, I have been doing some testing, and it looks like there are two distinct issues with FTP. Google Drive has it's own problems which I haven't tackled yet.
What I can do is limited since I don't have physical access to the machine that the webcam is on. About the only control I have over it is forcing an occasional reboot. The netcam server software running as a service (v188.8.131.52) seems to get quirky after a while even though the computer is otherwise very stable. It's 64-bit Windows 7 Home and it doesn't have the most reliable network connection (802.11g).
Yesterday, it worked perfectly all day long and then overnight, it failed to upload any of the recordings. They are good and I can play them through the web interface as well as the Windows client with VLC. I rebooted the machine this morning and the current recordings transfer just fine, but all of the failed ones never show up. They all have the synced checkmark set in the interface (FWIW, none showed in in Google Drive, either).
It appears that the behavior with FTP is try once as opposed to an actual sync like I am accustomed to with rsync. I don't see any way to force it to go back and re-attempt once it puts that check in the box.
The second issue is slightly more understandable and I am not sure what the solution is given the limitations of FTP. Once in a while, the computer will get rebooted during a transfer, which means that when the service restarts, it hasn't checked the synced bit, but a partially uploaded file exists on the FTP server. In that case, I get an obvious error in the log like the following:
FTPUploader: Upload: Remote file Recording_0_20170105_095702_664.mp4 is already exists
After this, the sync box is checked and there is nothing I can do. Deleting it from the FTP server manually doesn't force a resync later.
If there were a way to download the files from the server, I could kind of work around these problems, but I cannot figure out how. I can play them in the web client and the Windows client will open up VLC to play them, but actually downloading them seems impossible. Am I missing something?