Initially, problem appears to be fixed. I can hold the phone around an inch away from my face, at varying angles, while the screen remains disabled. Before, any cradling of my phone / shoulder would make the screen active, but now it remains disabled.

Just tested against a co-workers by placing on a flat table and moving fingers to cover up the sensor... mine seems to work consistently within about an inch of cover-up, his is hit-or-miss even while physically covering / pressing on the sensor.