Well done BMbikerider to have solved the problem. I too have a DUKA and think the mechanical shutter around the bulb is the weak point. It is a fairly flimsy bit of kit and can easily get damaged under constant movement.
The Colourstar 3000 analyser instructions say to cut out the light totally when analysing the neg for colour balance but in fact this seems to be impossible as even when the lever is turned to 0 some light escapes the baffle. OK at that very low level the analyser's probe seems unaffected but constantly turning it down to 0 or nearly 0 is likely wear out the baffle mechanism linkage
I find that safelight conditions for a meaningful period will only prevail if the lever is turned down to somewhere around 5. At that level the Colourstar 3000 probe readings seem largely unaffected and it avoids turning the baffle up and down.
As long as you can see to do the basics then the lower the level the better. The possible alternative with a DUKA is to have the level a bit higher but cover the front of the DUKA with a lid of a 8x10 paper box while using the probe
I am sure I have seen some claims that the DUKA is safe for RA4 at levels which practically allow a book to be read but alas I haven't found this to be the case.