Have a crossbow in slot one with a grappling hook. I take the grappling hook out and equip an arrow, and I can use whistles. I put the grappling hook back into my inventory and the whistle commands stop working.

In order to get whistle commands to start working again (which playing with the grappling hook) i need to put crossbow away, take out fists and punch something, then whistle commands start working again.