But i’ve got the solution.
This was linked to the problem of SABnzbd with long name paths.
I changed some options in SABnzbd and all is working fine again.
If you have some debug logs they would go a long way here, if it wasn’t enabled already then we’ll have to wait for a failure to occur again to see what steps Sonarr is taking and to lose track of that download.
If those were just posted then it might have to do with the retry mechanism.
Looking at NCIS.Los.Angeles.S01E11.HDTV.XviD-2HD I don’t see enough information there (only info logging) to determine what the issue might be, is there another release I should be looking at? The logs are pretty messy, but other failed downloads are being retried, making these issues look like something else happened, manually retrying, weird nzb only release that resulted in a new ID.