I had an ear break off of a nock during one of my shots this summer while practicing, first time ever, not sure what caused it, it did not seem like a dry fire at all, the arrow just flew about 10 feet ahead and off to the side and fell on the ground.
As far as the nocks fitting to tight on the string, is not a good thing in my opinion, I use a very small flat file on all of my nocks when new, the file just fits into the nock tight, I then pull the file through until the nock just bairly snaps onto my string.
I have read where others say the nock should fit loose enough to where if you point your bow to the ground with the arrow nocked and tap on the string the arrow should fall off, that for me is a bit to loose, you can just experiment filing your nocks until you find what works best for you. DK.