The next to smallest cog does NOT want to go on. The final one and all the larger go on just fine. The 11-speed I took off was all good. Checked the new 12-speed cassette against a couple of DT FH bodies and it slides right on. This happens with both a 105 and Ultegra 12-speed cassette.
Do I force the 11th cog on (hammer)? File something? Or is this not a compatible pairing (V1 FH body isn’t compatible)?