The interuptor switch only actvates to get alphas out of gear. Going
into reverse or forward does not activate the interuptor switch.

The gear design uses the thrust from the engine to force the gears to
stay fully engaged. The interuptor stalls the engine long enough to
overcome that effect when you pull it out if gear.

His stalling problem is probably that the cable is misadjusted or
streched so much that it is causing extra tension on the cable housing
and activating the interuptor switch.

N.L. Eckert wrote:
It could also be a problem with your interuptor switch.