This!...
What I think happened:
Until posting this I had forgotten about the predive drama that we had before dive 1. Our dive site was a completely exposed reef approximately 10NM offshore. We first got dropped off the boat in the wrong spot, and my boatman tried to tow us to the site. I have done this plenty of times when freediving, but never before on scuba. The extra drag from the scuba gear made holding on a seriously strenuous effort and ultimately made it impossible for the boat to turn us towards the reef. We got back on the boat and motored to the site and I didn't think anything of it at the time.
Looking back I think I was just too preoccupied to notice that my shoulders were giving me grief and that I had probably pulled some muscles while being towed behind the boat. Years ago I had shoulder issues from snowboarding that had accompanying fatigue, not sure how that works but I think that is what is going on here.
It has been a good exercise thinking my way through this and I am now far more prepared in the event that myself or my future dive buddy were to get DCS. I now have the NZ dive emergency # in my phone and I think I will be less hesitant to call it if I suspect any problems.
Two years ago I lifted 8 tanks from my car at the compressor station and yanked out steel doubles since they were heavy. That sealed my fate even before we got into the water that same afternoon, 4 hours later for a dive to 64m/210ft.
After recompression treatment and an MRI scan of my shoulder 3 weeks later, the doctors could see that the damage occurred in the muscle tissue (and fortunately nowhere near the bones). Thanks to posting my story here, I started considering everything action before the dive. And that's when it struck me....unloading tanks, even hours before the dive. That fact also made the doctors look closer at the muscle tissue and the answer was there.
Now this was a dive beyond the recreational boundaries, but a longer dive to only half the depth would have resulted in the same outcome.
Crossing the NDL is a gray area, since both tables and computers follow a pre-calculated model, based on an average diver. Many divers cross the NDL in real life while their computer says they're diving within limits. Others cross the NDL according to the computer while their body is still within the NDL.
Crossing the NDL is not like a switch from fun to drama. Knowledge and experience can turn fear into confidence, so it might be very interesting for you to explore that NDL border with an instructor during a course. From your description, you're ascending when you're getting close to that number on your computer. So you are already touching the border....