This is very common on the 2015 forwards on these dimes. We see it almost as often as other common events. When you look at Variety Vista's listings, most of the doubled dies end in the early 70's. Just a few on the new dies. But my opinion this is cause by die deterioration and also die polishing to to remove feeder finger damage. The dies are just abraided too much. Just a die event that and they continue to use the die.