I would check it this way. Pull the black 2 pin connector (black & white wire) near the E-box. Two things to check here:
Install lanyard and hold the "Stop" button down while checking continuity at the connector theat leads to the Star/Stop switch. If you have continuity, test again with lanyard removed and while NOT holding the "Stop" switch. If you have continuity on both tests your problem may be the connection between your stop/start and the E-box or it could be inside the E-box (unlikely). To test this, get a paper clip ready (bend in a "U" shape) and fire your ski up. Insert both end of the paper clip in the E-box side black connector and it should shut your ski down. If it does not, check your E-box internals.
If everything check out OK it must be your connection between the swith and E-box.