I've had a problem with the Files App when transferring video files from an iPad Pro to either a USB-C flash drive or an external USB-C drive.
The transferred video file is unusable for viewing from either the flash drive or the external drive using any type of video player even though the extension is m4p. Occasionally I get the same problem with pdf's.
It appears that using the Files App on an iPad Pro is only useful for transferring files to the iPad Pro, NOT transferring files From the iPad. Apple needs to address this. Why should the Files App only be good for transferring files to an IOS device?
Why not both ways??