I am having some trouble finding the cause of this issue.

My Episerver logfiles is filling up with this:

2017-03-20 11:56:42,916 ERROR [16] EPiServer.Search.RequestHandler.SendRequest - Update batch could not be sent to service uri 'http://localhost:17010/IndexingService/IndexingService.svc/update/?accesskey=local'. Message: 'The remote server returned an error: (500) Internal Server Error. at System.Net.HttpWebRequest.GetResponse()
at EPiServer.Search.RequestHandler.MakeHttpRequest(String url, NamedIndexingServiceElement namedIndexingServiceElement, String method, Stream postData, Action`1 responseHandler)
at EPiServer.Search.RequestHandler.SendRequest(SyndicationFeed feed, String namedIndexingService, Collection`1 ids)'
2017-03-20 11:56:42,932 ERROR [16] EPiServer.Search.RequestQueueHandler.ProcessQueue - Send batch for named index 'EPiServerFTS' failed. Items are left in queue.

And the search pages produce no results regardless of search query.

Going to http://localhost:17010/IndexingService/IndexingService.svc/search/?q=matsedel&namedindexes=default&offset=0&limit=20&format=xml&accesskey=local presents an empty list, matching the results I get on the websites own search page. This means the service configurations seem fine in general since it responds to GET requests.

But to fix this I need to know what causes the error for the "/update"-route.

Is there any way to get some logs for the service so it can tell me what is wrong?