The LCD diffuser comes with a white semitransparent film cover on the front of the diffuser. We originally thought that it would be OK to remove it, but it appears that this can cause the LED's to become loose, which might make the diffuser mounting less solid. The manufacturer seems to have glued the LEDs to this cover.
When installing the diffuser (manual page 24) please leave the front cover ON the diffuser. We have tested it and this does not reduce the light level any appreciable amount. It actually diffuses the light a little more across the display.
(If you have already removed it, that's OK. Just make sure the side
LED's are still mounted solidly.)