Unreal Engine 4.26.1
To demonstrate this I created a scene with a cube constrained above another cube. If it hits the ground and breaks the constraint, it fires the event, and prints “Constraint Broken Event Fired”
Calling BreakConstraint before the cube hits the ground only shows the “Performing Test” string. The constraint breaks but the event isn’t fired.
The test blueprint is a function that is marked as “Call in Editor”.
The constraint event is on the Event Graph of the same blueprint.
A workaround is to directly call the code following the event when performing a break. But the documentation does not mention that the OnConstraintBroken event is only called when the constraint breaks through forces, and not when broken through BreakConstraint.
My expectation was that the source of the break wouldn’t matter, or that the name or documentation would clarify the distinction.