Howtek D4000 Drum Scanner Update #2

Did some more cleaning these past few weeks since the last post and solved one problem, but ran into another. 

-Cleaned and cleaned again the pulleys for the drive belt. 
-Cleaned and lubed the lead screw again.-Cleaned and lubed the tailstock bearing.-Cleaned the same drum I had been using.-Re-did the DIY pads I had been using, slightly thinner so they were all within the small recess as the factory pads are. Before, some were slightly too wide which led to the drum not centering correctly on the tailstock.-Cleaned the dust out from behind the FOPI, on that lens. -Cleaned the lens on the other side of the FOPI, illuminator lens?

Now does 2K dpi scans with no hint of lines so that's a big relief. 
Next thing to suss out is now when I set 4K DPI in Silverfast, it always returns an F702 error when checking lumens. At 1K, 2K there is never a problem but at 4K each and every time it pulls the error code.
Sample shot attached:
Wartime black paint Anniversary Speed GraphicBlack paint Kodak Ektar 127/4.7HP5 in HC110 1:100 semi-standBlue painter's tape, dry mountedScanned at 2K DPI

Here is the result: