I performed another reset on my 500M about two weeks ago, but this time I left all the voltages at factory default, with the exception of VOL SUS, which I raised from 128 to 150, in order to eliminate all traces of the tiny purple dots on an all-white field.
I gotta say... My 500M now looks better than ever. No more red-tinted elevatated blacks. The black level is significantly deeper now compared to when it was brand new. Even better, when looking at black level test patterns, I see no sign of black crush.
The reset is just what my 500M needed.