Originally Posted by KCT1986

Is this happening when cross-chained (big/big)? If so, the angle of the chain may not be meshing with the chainring. A short chainstay frame dimension could play a part.

Don't know enough about the Rotor crank and rings to guess about much else. Things that would matter is tooth profile design, wear or burrs on the teeth, chainline, elliptical? ...

Cog teeth alignment of the new cassette and overall relation to the chainline could also play a part. Or a combination of a few of the above.