I seem to remember that if an S76A failed a PA check the usual first fix was to swap engines 1 to 2 and 2 to 1. A second test would often pass. I can only assume that airflow differences caused a difference between the engines. So does the S76C automatic PA system compensate for engine position? If not then there is a built in annomally.
A few years back I spoke to the CAA powerplant people ref an Allison C20b with a PA problem. They suggested that for accurate PA figures the engines must be heat stabilised. The result was that we checked again after a longish flight and the engine passed easily.