Here's a situation I ran into that I had to resolve by using a separate newreader.
I had a nzb for a 2GB download in 40 parts plus some pars. Unfortunately the first ~20 files were corrupted beyond repair.
The first 20 files were then reposted which gave me enough files to repair the entire download.
The problem occurs that since I have two separate nzb files I can't just download a par file and sort it out myself. I gave up after it renamed my good files the third time and just used another program to get the file I needed to complete the repair.
TL;DR: I want a right click option to break a file from the nzb grouped queue when the AutoPar acts fubar.