The tach on my 2018 V7 III Special broke completely loose today on the way to work and was bouncing freely in the gauge housing, so I've secured it with rubber bands. It has about 550 miles and I've had it two weeks. All screw bosses (I think there are three) broke off the back of the housing, and there is oil next to the broken bosses. Makes me wonder what the speedometer bosses are like, but I'll ask the dealer to look when I take it in tomorrow since it is under warranty.
Edit: My motorcycle was assembled in April 2018, and the tach was made in February 2018 according to a sticker on the back of the tach housing.