Thank's to Kees (K5BCQ) help, now the kit is working!
After all it was one of the most common "rf" issues.... power supply coupling. A simple parallel 2.2uF capacitor in the power supply sorted this one out. How can one figure this one out since the problem only happens when addressing memory from 0 to 7.... or going greater than 20Mhz...? Amazing!
Now it's time to put termination on the Si570, boxeit up and make some sort of fantastic radio around this nice litle vfo....
Tested the low end on this particular si570 CMOS and it can go as low as 4Mhz, that is 1Mhz for some types of SDR's. I'm going heterodyne anyhow... bellow 4Mhz will go with an upconverter.