I am having a similar issue. Also new to Sonarr, so the only version I’ve had installed is 2.0.0.3934 (Linux).
The difference is that the errors (rolling every minute since Monday) seem to be only for episodes that I recently started downloading outside of Sonarr since the episode number of the download didn’t match what Sonarr thought the episode number was (Sonarr manual search came up blank). But, according to the history, the download was picked up by Sonarr – if memory serves me correctly, this was after I renamed them in the downloads folder to match Sonarr.
But anyway, back to the persistent errors – nothing in the queue, they all have import events, but no grab events for the reason described above.