Preparations of remeasurement of the Eötvös-Pekár-Fekete (EPF) experiment for the Weak Equivalence Principle were reported in [4]. Here we give a brief overview of the gravity field bias and try to estimate its possible effect on the EPF experiment. We report our first test results in the solar gravity field with Cu-Au and Al-Au pairs. The estimated errors were at level 2·10⁻⁹, the same accuracy that was obtained by EPF. We also found that angular positions of the balances showed good correlation with bandpass-filtered air pressure variations hence Wiener filtering may significantly reduce this correlated noise. We did not detect any deviation from the equivalence principle considering the estimated measurement error.