Have a brand new Ultegra 6700 groupset with a nagging issue that I'm hoping you guys can help out with. While I have a low post count, I have built several bikes before from the ground up so I am not totally new to this.

The issue is a minor chain skip in most gears but is more pronounced in the middle of the cassette. I can visibly see the chain ride up against either the next larger or next smaller cassette cog (can't quite make it out which one) and settle down in the cog again. When this happens there is a click that I can feel throughout the drivetrain. Pedals, bb, rear hub all turn smoothly with no clicks so I am certain it is caused by the chain and/or cassette.

I have adjusted the RD to try and center it on the cassette cog but the noise is still there. I tried reducing tension to where the RD almost wants to shift down to the next smallest cog and increasing tension to where it almost wants to shift up to the larger cog but I still see the chain skip in both extremes. I have also used my finger to manually push the RD so I could try & center the chain against the cassette cog but the chain still skips. This is not cross chaining as it is in the middle of the cassette.

In summary:

Problem: Chain skips in center cogs of cassette & small or large chainring

-- CS-6700 cassette, CN-6701 chain, RD-6700 RD, Easton EA90SLX hubs with 10 speed spacer installed (all new)
-- Chain is installed correctly, logo side facing outwards
-- No kinks or stiff joints in chain
-- RD adjustment appears right
-- Cassette cogs have the correct spacers between them and seem straight. Cassette is on tight, no play at all.
-- RD hanger is undamaged and as far as I can tell, is straight

Any ideas?