ok well first things first you dont need that cast node that you have in the widget (in the current implementation). also the way you are getting the health is a poor way to accomplish it since you are getting all actors of a class( this could cause issues).
why are you not using the built in damage systems? there are nodes for apply damage and event any damage. if you were to use those you could create a much more dynamic scenario.
to start try cleaning up the widget and see if that helps. if not we can work from there. or you could just set the value of the health bar manually as pictured below. make a variable on the health bar and bind that to the progress bar percentage. then whenever damage is applied just update the variable.
