Hard to pedal my new neo 2T

Hello,

I have a new neo 2T and found it hard to use. The first pedal strokes feel very slippery and my neo 2t does not run smooth. I have replaced the body to an xdr body for use with 12 speed sram force axs with 142 mm thru axl. I am in a quiet good shape but its hard to maintain 150 watts. Also their is a little wobble in the cassette. Its thightend firmly but it spins with a bit offset. 

Thanks already for the info