What do you see on the screen when you play the test record? Do you mean the output of the cartridge/phono section is too high and there’s clipping/overloading the input of the soundcard even when you reduce gain to its lowest adjustable? If so, the gain can be further padded down by putting resistors in between the phono section and sound card.
I had this problem too. Everything worked fine after I made the adjustment. A tech could help you get the right value of resistors for your phono preamp and sound card.
It’s worth it. The Foz works fine for crosstalk measurement balancing but does not also match phase as Adjust Plus does. Both are important!