LO limitation on the TES gui adrv9009


I am using the adrv9909 evb on top of the z706 board,

and i found out there is a limitation on the LO's lock frequency,

for some reason using the Rx channel with 122.88 MSPS and 100 Mhz RF won't let me configure the LO lower than 110 MHZ

(i am using the profile configuration wizard for the profiles generating)

can someone explain to me what is the problem and what i need to change for locking on 75 Mhz LO ?