I had an intermittent problem with the camera when our van was brand new. It went back to Autosleepers no fewer than three times to get it fixed and on the third attempt they found a dodgy din plug connection close to the camera. It just needed re-seating and it's worked fine ever since.
There is also a similar connection at the monitor end, although you seem to have eliminated that. To get to the monitor plug means removing the parcel shelf, not a job for the feint hearted, particularly if you have Remis cab blinds installed.
I'm not sure about the camera end on your Broadway, the the plug on ours is behind a trim panel, just behind the camera.
There is also an intermediate plug and socket which is located under the driver's door step. This is easy to get at and may be worth a look.
Of course there's also the 12v supply. It's obviously ok at the monitor end as you're getting a blue screen. It picks up the supply under the driver's door step and I seem to remember that it supplies both the camera and the monitor from this point.
I suspect that you've either got a duff camera or that the camera connecting plug is faulty, probably the latter.
On our vehicle the camera is wired so that it displays a picture all the time, not just when reversing. In my opinion it's a better arrangement, not only do you get an unobstructed rear view but it also resolves the delay in getting a picture when you select reverse.