This is a very generic error message and the SharePoint error log does not give a lot of extra information.

Yesterday, testing a ‘send to’ connection to a record center, we kept getting this message only when trying to submit a documentset. We had no problems submitting individual documents.

The solution is that you have to create at least 1 routing rule in the ‘Records Pending Routing’ library that you are sending your documentset to. After creating the rule everything worked as it should.