Yeah got that bit & the reason why it happens is the nut on the bolt grabs on one surface of the washer in turn the washer grads the face of the nutsert & as you turn the nut the whole lot starts turning together which means your winding the the nutsert back off the bolt at the same time.....
By using 2 washers with a little grease in-between them should create a point of least resistance so in theory when the nut on the bolt grabs the surface of the washer & starts turning it, it should just slip against the second washer instead of turning the nutsert.
As I said though its only "in theory" & if you play with these things at work I recon you could test out my theory for me & let me know if it works......
Cheers Old mate.