RE: dual switching BECs into Power Expander?
Since the problem seems to go away with the Equalizer 3D I am thinking that Hitec did not terminate the signal line correctly (Futaba made the same mistake with the 9156 and 9157 which it seems they corrected as the newer ones shipped don't exhibit the bad behavor the originals did). You are probably seeing "ringing" on the servo control line. The Equalizer 3D has less drive than the MZ so you would get a slower rise and fall time on the signal edges and not as much ringing. Not much you can do about this except to put a 220 - 330 ohm resistor in the signal wire near the MZ end of the extension on all the servos.