bored117 

Just put on Ultegra DI2 last night... fiddled around a little but was getting late so I hit the sack.
One thing that was strange was... I was having issues shifting from 10th (smallest) to 9th... It just won't do.
Other up/down works just beautifully which has me a little stumped... (9th to 10th, 8th to 9th, 9th to 8th all works fine... and rest of range as well)
What could it be? Definitely not cable tension
Some insight would be awesome. Thank you!

fietsbob

begin at the foundation base .. checked that the derailleur hanger
is spot on for alignment ?

I_like_cereal

Your first problem is the Di2.

If there is not cable then you need to look at:
The wheel is it centered?
The rear D is it adjusted properly H and L screws?
Chain?
Cassette?
Front D?

bored117 

Everything is spot on (Hanger/Wheel/Chain)... I think I figured out the issue.
Changing wheel did nothing, however, changing cassettes made it work just fine... I think this particular cassette either is defect (didn't bother measuring depth on caliper yet), or just incompatible with my setup. More prone to think it's bad cassette. Thanks guys.

I_like_cereal

If it is SRAM and not ShimaNO then that would be the problem. It could also be a Dura-Ace v. 105 issue as well. ShimaNO designing the high end to work only with the high end.