I have tried changing the channels but even through different drivers it still happens.
So this points to your wiring, not so much the actual connections but the way the wires interact with each other inducing signals in the other channels. You could try making the wiring of the two channels a lot neater so they are not so tangled up with each other and are kept separate as much as possible.This effect is also known as cross talk.
Does this 'cross talk' happen even if there is no display of it when one is off and the other is on? Ie. when one channel is on, none of the other channels LED's come on showing it leaking across channels.
So this points to your wiring, not so much the actual connections but the way the wires interact with each other inducing signals in the other channels.
The trouble is there are so many LEDs and connection points i found it hard to do it any better.
Then the project is beyond you.
Seems to be a LED wiring problem.Are the LEDs on a star base?Asking, because I once had a short between the LED and the base of a 3watt LED chip (normally isolated).Leo..Edit: just saw the image.Check if mounting screws are not touching/shorting the LED wiring.Can your 48volt supply be turned up one or two volts (most open frame supplies have a pot).Or, temporary short one LED in those strings, to lower total Vf.