Roll servo is likely under your left foot, but can be elsewhere... Had
a newly installed S-Tec 50 in an Aztec that had all kinds of teething
problems with oscillations... Finally solved after months of struggle
when S-Tec physically changed out the components on the amplifier
board... My suggestion is to take it back to the installer or to a
radio shop that is familiar with S-tecs...

Denny