Why does the barrier arm bounce or creep when it reaches its stop?

Bouncing or creeping at the end of travel suggests wrong balance. Springs soften over thousands of cycles, someone may have changed the boom to another length, or an added light strip or skirt increases weight. Worn pivot points play a part. We measure spring tension, boom weight and mounting, then reset the geometry. A badly balanced boom overloads the drive, so deal with it early.