FYI, your flickering issue might also come from LED lights. The 50/60HZ correction (as far as I know) only corrects for some old school fluorescent ballasts that operate at mains frequency. I was just reading that incandescent might have flicker too, since they get hotter as the amplitude increases, but I have never seen this personally, but don't doubt it can happen.
Some LEDs use pulse width modulation to control the brightness (dimmer switch), or to prevent burnout (lower heat production) while over-driving the LED. My cheapo LED lights I had in my enclosure caused flicker even with the flicker reduction settings (50/60HZ) enabled. Eventually I tracked it down to the LEDs themselves, since halogen lamps and incandescent showed no visible flicker whatsoever.
It is a pain in the butt to figure out what frequency any particular LED's PWM operates on, but something on the order of 5KHZ+ should work fine. I eventually found some LEDs that operate at many KHZ, and I now have zero flicker. I went through 3 other LED panels before I found one that worked, so buyer beware.