The reason why he went to Vader's ship to take the blame for losing the Falcon was due to writer's fiat. The character did this for no other reason than the writer's of the screenplay wanted him to. When all other organic reasons for an event occurring fail and a choice of action takes place which makes no other reasonable sense, the only logical way to understand the event is to realize that the writer's simply wanted it to happen that way.
The screenwriters on Empire were very talented people. If they had wanted to, they could have written a more satisfyingly organic reason for his actions. Perhaps his duty roster included someone who Needa knew was incompetent, but Needa allowed them to undertake the scan. An answer like that would have been more likely to have occurred (never ascribe to malice what can more easily be blamed on incompetence) and it would have felt more organically honest. However, it would also have taken too much time to lay out as a sequence, time that the producers evidently did not have. So in the end, the reason why Captain Needa did what he did was all because of timing.