Has anybody considered airflow reversal over the helideck at low level? I encountered this many moons ago whilst approaching a North Sea platform in a Bell 212 at close to max gross weight. In the last 20-30 feet of the steep approach, the rod suddenly increased and the aircraft made a "positive arrival" in the middle of the helideck despite the smart application of full power.
Investigations later on showed that with a 10-15 knot wind from a particular direction, due to the obstructions around and under the deck, including eflux from some turbines, the airflow over the helildeck curled steeply backwards over the downwind side of the helildeck producing a 10-15 knot tailwind in the very last stages of the approach.
Had I been using the low & slow or "fast and furious" technique, the outcome might have been much the same as the one in this thread.
It's not possible from the photos to see whether there is an air-gap under the helideck, but has anybody looked at this aspect?