If you can'r find anything wrong with the bow and it still shoots fine then that's good. Now the issue of the nocks themselves. It could be that that nock was damaged. It could also mean that if they are too tight on the serving you are forcing it on the string. This spreads the ears and could weaken them. Maybe CE had a bad batch, which can happen from time to time. For the money I wouldn't push it and replace all the nocks just as a precaution, which isn't a bad idea to do periodically anyway. Maybe once a year.
Another thing I would do is have the string reserved with slightly smaller diameter serving so that the nocks aren't so tight in the first place. Serving comes in different sizes, the most common for cneter serving being .018", .021", .025", etc. Believe it or not a couple thousandths can make a huge difference, not only in the fit but in accuracy also.
If You're Not Living on the Edge You're Taking Up Too Much Space
Martin/Rytera Staff Shooter
PSAA Life member, UBP Life member
PADI AOW Diver