Files : Large data transfer to USB 2.0 HDD timeout

During a large data transfer (35GB) from my local drive to a USB 2.0 external HD, the transfer consistently times out after only a few gigabytes. I've tried two different external USB 2.0 drives and have the same issue. The drive seems to go into power-save mode as if it was no longer being accessed. The transfer dialog shows that the data transfer is still in progress but never moves after the drive times out. When I access the drive from another Files window, it will spin up and display the directory as expected, but the transfer never resumes. This has been tried with a Western Digital USB 2.0 external drive and a Seagate drive.