A TV episode showed the same group’s release 4 times, across 3 different indexes. Two were larger (contained Par2 files), and two did not. All showed the same age, and full title. Sonarr grabbed one of the two smaller NZBs for the group’s release (without par2 files), and failed because repair blocks were needed. Sonarr then blacklisted all 4 NZBs.
I happened to perform a manual search for the episode, and was able to force Sonarr to grab one of the larger NZBs (with Par2 files) and successfully download the release.