When the disk was empty, backing up a Sandisk Extreme Pro 64gb was just as advertised. A complete 64gb card would take up to 20 minutes long to back up. I have copied some stuff to the MPWP via USB, reaching half of its capacity but now a 64gb card back up takes up to 4 hours long! This problem turns the device into a cumbersome option to backup video in the field. Any help will be highly estimated! Thanks!
I would suggest you to ensure that the device firmware is updated.
Refer the link provided below to update the firmware on the device.
Diagnose the device by running test to determine the optimal health of the device which could affect data transfer.
You can also check the SD card for virus or malware which could be affecting the data transfer speed.
@eduberth Disable Twonky, Plex, Reboot the MPW device and do the SD Card Import again.
IE: reduce CPU and Memory usage