I think I know what you're after. You want it like "Hold click onto the button to keep the LBumper and RBumper up, then letting go would reset their angle"? If so, here's an explaination.
Your click events are triggers ("On Click"), this means that those events will run only once, then it gets to Event 3, which resets the angles back to 0.
Try changing Events 1 and 2 from "On left click" to two conditions: "Left click is down" and "Is mouse overlapping spr_LBumperCont". Then remove the "Every 0.25" condition, then move Event 3 above Event 1, so that the order will be correct (It will read if it should reset the Bumpers' angles, THEN it will detect if it is being clicked, and if it is, then reset the angles)
Hope I've understood you and have been of help! Welcome to the community!