It’s a bug.
As mentioned in Desired sample rate to best sample rate for mini v2 - #4 by ricardas
CGEN as to be at least 5 MHz, so according to the equation using oversample of 2, brings it to only 2.19MHz, you need oversample of at least 8, to have CGEN more than 5MHz. Sample rate does not need to be harmonic of any number.