Nvidia Shield Pro 500GB, windows 8.1 USB file-transfer issue

Nvidia Shield Pro 500GB,
Windows 8.1
USB file-transfer issue, System is connected but copies fail mid transfer. Small transfers go ok, but anything over a few megs gets interrupted.
Device is in Dev Mode.
Tried to replace default USB drivers with the ones from website, but no 64bit win8.1 drivers are found in the inf.

You may need to manually add your device’s USB ID to the driver ini/inf file if it isn’t found as long as you know you have the correct driver file. Check Google for instructions on doing this for Nexus phones, it should be a similar process.