I've never been a ride op, so I don't know much, but this is just going on common sense: If they felt that something was wrong and they felt the need to send a test train with no guests, they maybe should not have loaded another train WITH guests until that train had come back into the station safely, and/or been inspected, and a problem had been ruled out. Somebody knew something wasn't quite right. They sent a train full of guests anyway. That in itself seems like operator error. Maybe not the crash itself, but the decision to send guests when a train was testing.
Not blaming the ride op. Just saying that maybe clearer policies about testing/loading should be made known in the future.