I have been managing since with the SD but it is somehow sensitive to the working order. After bootup, the SD is placed and then one can use it. If it is already there while booting, it will usually not work but creates an error. Then it needs to be removed and replaced, then it might work again.
Otherwise, the KC901S seems to work fine. However, sometimes I manage to make it hanging and need to a forced restart.
it now can go down to 0 Hz which sounds good, but measurement error at this ultra low freq still not fixed so this feature is still rather useless, for example its still cannot show impedance of a DUT correctly (other than 50 ohm load), the same with magnitude and phase of gain and loss etc.. fwiw.. looking forward for the next FW update, thumbs up anyway..