My LB button only works when pressed firmly (ocassionaly)

I only bough this controller a few months ago and all of a sudden the LB button only works when pressed down very firm. I play games that rely heavily on it so I assumed the bumper would have snapped/cracked but if I put the very same bumper in my old controller (also model 1780) the LB button works fine on that (although over things aren’t functional on that controller)

From the look of things within the controller I can’t see anything that’s snapped off/broken. When pressing the LB it feels kind of loose too, even though it’s properly in place.

Thanks