alright so my bike is screwing up. i only had it for about a month and couple weeks but i tried to do hops(new to bmx) and my handle bars slide backward. the silver part that hold the bars connecting to the other side of them, the hole in it, the handle can slide! they can go as if those pro bike things like all the way forward or backwards to my waist. i got it from walmart though for like 80 bucks. its a NEXT bike. heavy but i can lift but when i try a hop i come down and the pressure from my arms slides them down. what do i do?!