OK, parts got in and after a couple of hours of wrestling I got the scanner to talk to my Win10 64 bit pc. It's working currently, but no guarantees whatsoever it'll be that way next time I fire it up, so I grabbed a quick screenshot of the pertinent part. I'll include some instructions on how to get there in case someone stumbles across this post later on.
This dialog is accessible from the FlexColor program; to get here, do this:
* Fire up FlexColor and ensure it's connected to the scanner.
* While in the FlexColor main screen, type the letters "debg" on your keyboard. Nothing will apparently happen, but this is crucial for unlocking the service menus.
* Now go to Maintenance -> Monitor window
(Note that you don't get this option unless you have done the 'debg' thing!!)
* In the Monitor window, you can modify various parameters as shown above; you can see the settings I used to get the plot shown. The 4x5" setting next to 'Frame' will generally show the 'ugliest' plot because of the light falloff/large scan area etc.
Note that in the plot I show above, the color channels track quite well. There's no conspicuous bump in the red channel as shown in your plot:
(yours is the bold set of plots on top, mine are the narrower ones at the bottom)
My plot does show more irregularities which I assume is just dust. IDK when (if ever) this scanner was cleaned out.
I may open it up one of these days to have a look inside. First I'm going to see if I can get it to talk to the computer reliably.