@pastthepoint There is nothing obvious pointing to why this board failed so we will replace it under warranty. It will be good to get the board back to see what is loading the 5V rail in this way. Please send an email to warranty@duet3d.com and reference this thread.
As I already mentioned the two most likely things i have seen to cause this in the past is something faulty on the 5V or a stepper motor fault that ends up blowing the driver (and internally the driver shorts 5V to ground). Please make sure your extruder and stepper motor are grounded.