[Richy99]

incompletes can come from many things on newsgroups

the server that the person using might not be very good
the peering arrangement that is used by the poster/ntl
the poster has fubar'd the post when posting
retention of the server (VM's end)
how busy the group is

now dont forget this is a free service and you cannot expect good results from a free server and the shear volume of nntp traffic and the subsequent bandwidth use doesnt make it profitable to keep the server working like commercial ones