BC operator Helijet had a nasty incident last November with one of their four HEMS S-76C.
Shortly after uncoupling the AP at 600ft on night-time finals the crew got into a high rate of decent (between 1100fpm and 2500fpm, depending on who you believe) and allegedly lost so much NR that the generators went off-line. They did however manage to recover but the casualty they were flying to pick up had to wait for a fixed wing transfer the next day.
More details here.
The paramedics union are fairly grumpy about it.