The unit is randomly not syncing all data from the Nexto to the USB drive. It seems that the folders that are not copying have been named with a TMP filename, even though they seem to have been transferred from the card to the 2901 correctly, without error. For example, one of the folders is named TMP00001.199.35CF
The folders that have been named correctly through the card-Nexto transfer with the normal date stamp method are copying fine.
I have already tried re-formatting both the USB drive and NEXTO and also using a different USB drive but having the same issue.
Having TMP folder means SYNC was failed.
ND2901 make every file list before actual data copy under that TMP folder. Then if data copy done successfuly, the TMP changed to normal date coded name.
Fail on SYN usually caused by power compatibility.
Supply power to your USB drive separately by USB Y cable or similar.
Then it will work.