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.