I dont know what is causing but i tried tons of fixes, i mainly use public torrenting, and sonarr and radarr are doing it.
I added *.arj and arj to the quality profile avoid list without success, and prowlarr is as torrent (i’ve read sometimes it gets confused and uses nzbget)
You can try adding cleanuperr to your *.arr stack. It will listen to your queues and if something gets stuck, like .arj files, it’ll remove them, blocklist them, and maybe re-search? I’m not sure.
You can also change your settings in sonarr to not do any rss sync searches with your public indexers. This stops sonarr from seaching those indexers automatically for the next release. I’ve notices most of that garbage pops up before the official release, then gets drowned out by the real stuff after the release. If you leave the auto/interactive search enabled, you can just click the auto search button for the episode the day after it comes out. You likely won’t pick up any garbage this way.
I wrote a script that spam reports these, and I run it when I’m feeling frustrated with a something, but nothing I’ve spam reported with the script has gotten taken down yet. So, that sucks too.