if i'm not wrong, i think the red light camera do not go off
within about 1 seconds after the lights turn red.
this is to allow time for those vehicles that are already very
close to the line and it would be more dangerous if the driver
applies the brakes very suddenly.
anyway, you can notice that when the lights turn red, the other set
do not turn green immediately, it'll change colour in about 1-2
seconds later.
hope i'm not wrong, as for the light you see, could be the
reflection from another car (if you're travelling in the day)