It's displayed in System: Info within Sonarr.
There will be grabbed events and imported events (among others in History).
Based on the logs:
17-12-9 05:56:45.9|Warn|ParsingService|Unable to parse episode info from path /volume1/downloads/sabnzbd/tv/c941cfc7cd254451956f85f645532928.mkv it looks like NZBGet is not using job folders or TV sorting is enabled and the file is being extracted to a location without a subfolder named after the NZB.
Each download should have it's own folder, named the same as the NZB (which is shown in the UI of NZBGet), that way Sonarr will only import files for the correct download and has the folder name to get additional information from (in this case the series, season number, episode number and quality).