I have the same error. If you click the filter from bug to warn, for me, all of those errors are preceeded by
HTTP Error - Res: [POST] http://<IP>:8282/command/upload: 500.InternalServerError
Error: Could not add torrent to session.
Looking inside the file log I see
18-3-21 10:24:01.5|Warn|HttpClient|HTTP Error - Res: [POST] http://<IP>:8282/command/upload: 500.InternalServerError
Error: Could not add torrent to session.
18-3-21 10:24:01.5|Fatal|NzbDroneErrorPipeline|Request Failed. POST /api/release
[v2.0.0.5162] NzbDrone.Core.Download.Clients.DownloadClientException: Failed to connect to qBittorrent, check your settings. ---> NzbDrone.Common.Http.HttpException: HTTP request failed: [500:InternalServerError] [POST] at [http://<IP>:8282/command/upload]
at NzbDrone.Common.Http.HttpClient.Execute(HttpRequest request) in M:\BuildAgent\work\b69c1fe19bfc2c38\src\NzbDrone.Common\Http\HttpClient.cs:line 94
at NzbDrone.Core.Download.Clients.QBittorrent.QBittorrentProxy.ProcessRequest(HttpRequestBuilder requestBuilder, QBittorrentSettings settings) in M:\BuildAgent\work\b69c1fe19bfc2c38\src\NzbDrone.Core\Download\Clients\QBittorrent\QBittorrentProxy.cs:line 225
--- End of inner exception stack trace ---
at NzbDrone.Core.Download.Clients.QBittorrent.QBittorrentProxy.ProcessRequest(HttpRequestBuilder requestBuilder, QBittorrentSettings settings) in M:\BuildAgent\work\b69c1fe19bfc2c38\src\NzbDrone.Core\Download\Clients\QBittorrent\QBittorrentProxy.cs:line 241
at NzbDrone.Core.Download.Clients.QBittorrent.QBittorrentProxy.AddTorrentFromFile(String fileName, Byte[] fileContent, QBittorrentSettings settings) in M:\BuildAgent\work\b69c1fe19bfc2c38\src\NzbDrone.Core\Download\Clients\QBittorrent\QBittorrentProxy.cs:line 98
at NzbDrone.Core.Download.Clients.QBittorrent.QBittorrent.AddFromTorrentFile(RemoteEpisode remoteEpisode, String hash, String filename, Byte[] fileContent) in M:\BuildAgent\work\b69c1fe19bfc2c38\src\NzbDrone.Core\Download\Clients\QBittorrent\QBittorrent.cs:line 58
at NzbDrone.Core.Download.TorrentClientBase`1.DownloadFromWebUrl(RemoteEpisode remoteEpisode, String torrentUrl) in M:\BuildAgent\work\b69c1fe19bfc2c38\src\NzbDrone.Core\Download\TorrentClientBase.cs:line 189
at NzbDrone.Core.Download.TorrentClientBase`1.Download(RemoteEpisode remoteEpisode) in M:\BuildAgent\work\b69c1fe19bfc2c38\src\NzbDrone.Core\Download\TorrentClientBase.cs:line 117
at NzbDrone.Core.Download.DownloadService.DownloadReport(RemoteEpisode remoteEpisode) in M:\BuildAgent\work\b69c1fe19bfc2c38\src\NzbDrone.Core\Download\DownloadService.cs:line 69
at NzbDrone.Api.Indexers.ReleaseModule.DownloadRelease(ReleaseResource release) in M:\BuildAgent\work\b69c1fe19bfc2c38\src\NzbDrone.Api\Indexers\ReleaseModule.cs:line 67
at NzbDrone.Api.Indexers.ReleaseModule.<.ctor>b__7_0(Object x) in M:\BuildAgent\work\b69c1fe19bfc2c38\src\NzbDrone.Api\Indexers\ReleaseModule.cs:line 46
at CallSite.Target(Closure , CallSite , Func`2 , Object )
at Nancy.Routing.Route.<>c__DisplayClass4.<Wrap>b__3(Object parameters, CancellationToken context)
I am using:
Sonarr: 2.0.0.5162
qBittorrent: v4.0.4