Did I read your other thread right? That you had served the string with 30# monofilament? If so then that might be part of the problem. Nobody uses mono any more; haven't for decades now. I remember when I did that I used 12# mono. The size you need depends on the string material being used and the number of strands. Saying your string is 16 strands doesn't tell us much because we don't know what material the string is made of.
In any case, I know hutch mentioned filing the nocks to open up the throat, but this is not the best solution as you can never file two nocks exactly the same. You need to find the right size serving material (fastflight) and serve with it. And you don't need to serve the whole string to protect it as you are now doing. The more serving you put on the string does nothing but add unneeded weight to the string and slow down the bow. Besides, having so much serving on the string can actually hide broken strands and at some point the string could snap without you having been able to see it before hand.
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