It's the nature of the beast, though
If a client is outsourcing something, then it frequently means that they want a particular solution, but don't have deep expertise in that solution.
Which means their understanding of the solution they've chosen is limited.
Which means that if something goes wrong, they are limited in evaluating HOW it went wrong. The unscrupulous will just blame the contractor for doing what he was told to do.
After all, the usual story a contractor will tell you is making a support call, looking at the client's equipment, and saying to himself, "Holy mother of fuck, what have these people been up to?"