Nockturnals not staying lit...

[Kirby86]

Of the last three animals ive killed, two Nockturnals came loose from the arrow, and the last one broke off on a hard hit on bone. None of the three have stayed lit after the shot.

I checked the ones ive got left and theyre snug...but they arent as tight as my unlighted nocks. Im shooting muddy ht-1s (micro-diameter ,
.165 shafts)

Am I having nock pinch or what?