Modified servo only turns in one direction

Hi all,
I just modified an HS-422 servo for continuous rotation by following the instructions.
But then I tried to adjust the default position by sending 1.5ms pulses (BS2 program with a PULSOUT 14, 750 loop), and when I adjust the potentiometer, it only starts moving in one direction, and doesn’t change it even when I move the pot the other side around…
So then I tried to stick the pot at a position where the servo stops moving, and then I sent 1.3ms pulses, in which case it goes fast in the usual direction, and 1.7ms, where it stands still, without moving.

Any ideas of what’s happening? Did I do something wrong during modification?

Thanks in advance,
Alberto