Ernie Ball Sub 5 Question

Hey Everyone…I just got a new to me sub 5 (see pic). Plays great. I have one small issue. The pick up bounces up and down fairly easily so much so, that when playing with my
fingers, it can move when I reach for the higher strings. Any ideas? I’m thinking of replacing the spring behind the pickup although I honest have no idea how to do that. Thanks for any help. Rob