Cassette/race wheel problem for the mechanics

What kind of dropouts?

Your dérailleur hanger might be bent ...... is it completely vertical or does the cage portion tilt in toward the spokes??

Is your chain too short? Have you adjusted the derailieur gears to move farther from the cassette? Are you using the correct spacer when you install the casssette onto the hub?

horizontal and adjusted just fine i think

no, it shifts fine, the chain doesn't run smoothly from the pully wheel to the cassette for some reason

seems to be straight and runs fine with other wheels

length is fine.....the spacers, i thought of this, but don't know 100% for sure where the spacers should be (since they don't go between every cog, correct?).....either way I run it with the same configuration on my training wheel and have no problems

The only thing I can think of is to tighten down the b-tension screw more to move the pulley further from the 27 tooth. Thats really the only other thing you can do.

that was my first though, however when i tighten the screw nothing seems to move

Sounds like a spacer issue. The 12-27 might be too close to the hub on your race wheels and OK on the training ones. Threfore, the derailleur isn't getting up far enough to place the chain on there. I had a tough time with my Spinergy wheels getting it figured out as to whether or not to space them (I needed it).

Pilot error: Did you stack it on the freehub correctly? Take it off and reassemble. Rule this out. I buggered a SRAM MTB cassette once b/c the spacers had pins and I didn't slot them. Drove me nuts until I started over and saw it.

Are all 3 cassettes the same manufacturer and model? If the 12-27 isn't Shinamo or is 105 and the others are DA, that might contribute?

Compact crankset? Are you at/over recommended capacity for your RD and need a medium or long cage? You might have gotten away with it with the other wheels, but after you get to big enough differences, the short cage isn't sufficient. Check shimano.com or your install instructions for your RD to see if you are.

When you tighten the screw, you should visibly see the derailiuer gears move downward, away from the cassette.... if thats not happening, something is screwy with your RD.