RF Block Set RF Filter transfer function changes with sample time

Implemented a chebshev low pass RF filter in RF blockset:

filter order: 3 ;

pass band frequency: 10MHz ;

pass band attenuation: 1dB ;

Input frequency: 1MHz, 5MHz, 10MHz.

From filter visualization: attenuation at the above 3 frequencies is 0dB, 1dB, 1dB.

If I set RF config sample time to be 120MHz, the simulation result at the above 3 frequencies is 0dB, 1dB, 2dB.

If I set RF config sample time to be 480MHz, the simulation resutl at the above 3 frequencies is 0dB, 1dB, 1dB (same as filter visualization)

It does seem it has to do with circuit envelope algorithem.

Can some one shed more lights?

Thanks,

George