This sounds bad to me, I've used the camera for 2 months always on 60p on the previous firmware. The quality improved with 1.2, is a lot more sharper but noiser with much green tint on low light and with flickering.This is probably an issue with your camera or your camera settings and not an issue with 1.2. I am on 1.2 and am not experiencing the issues you describe while filming in 1080/60.
I don't think is the case to reflash it again...settings are default and on 50Hz.