I think Event 3 needs one more condition. "Is Not Crouch Attacking".
It was freezing because Event 3 would set its animation to Idle first, and after that you'd change it back to CrouchingAttack. Since this would happen every tick, it would never get the chance to go to the next animation frame.
These events are prone to such errors though. I would suggest trying to use more sub-events and Else conditions for neater logic. For example:
On N Pressed
Player Is Standing
Do standing attack animation
Player Is Crouching
Do crouching attack animation