I don't have experience with that brand but use similar equipment as I have a GenII hand scanner.
The illuminator is too strong and washing out the picture.
You said it is a long distance illuminator but you are using it at 40 yards?
I have a similar problem with a Streamlight TAC IR illuminator.
It is fixed focus and single power level.
It over saturates the picture a little at 100 yards but "sees" well out to 200-300 yards.
I use an Evol T20 I picked up off ebay for 30.00 delivered.
It has multiple power levels and focus and is almost identical to a famous brand that sells for almost 200.00.
It is also 850nm frequency and is second from left in pic below.
L-R Sightmark 850nm, Evol T20 850nm, Streamlight Super TAC IR also 850nm, Chinese Torch with 940NM pellet installed.