I've not read through this but it turned up whilst I was searching for something completely different but here's my experience with ND.
Thinking I was warming up into CCR I bought a Azimuth SCR from ND in 2002. I did the course with an instructor that was, well, not very bright (an example of this was a drawing he made explaining how the scr worked showed exhalation pipe leading directly into tank - I didn't bother to correct him, he never noticed).
I took the unit to Stoney for a play with a mate who was on a twinset. The flowmeter, whilst a lovely build quality wasn't sufficient to measure flowrate at 40m, I wasn't going that deep so set up, tested connections and jumped in. No problems at all. Second dive, I rechecked everything, much to my friends impatience, jumped in - at 10m signaled ok to buddy, then started sinking rather quickly. Thinking it was counterlungs compressing I injected, to no avail. Ended up on the hydrobox with a completely flooded unit - switched to bail out just as water was being delivered through mouthpiece. Just got back to surface with no air left.
Buddy explained that after I signalled ok, I looked down and as I turned my head the exhalation tube come off of mouthpiece. It was held on to a smoothbore and with a single cable tie. I boxed the unit up, declared it unfit for use and sent it back to ND. I received it back from them with TWO cable ties on it - hardly restores my faith in the unit. I finally got some money back minus a very hefty restocking fee of a couple of hundred if I remember correctly.
I've actively dissuaded students and anyone I meet from purchasing anything more than a snorkel from Northern Diver ever since. I'd not wipe my ar...bottom with anything that comes from them. You can find me at most dive shows walking past the ND stand whilst slagging them off. Feel free to say hi.