I also have a new 4011, and it's a crappy mounting design in my opinion. I added some double sided foam tape to the inside of the bracket which firmed it up a bit.
RB4011iGS+, RB750Gr3, RB750r2, CRS326-24G-2S (in SwitchOS), CSS326-24G-2S, CSS106-5G-1S, RB260GS
Not sure if I beat them in submission, or they beat me into submission
Warning: I know enough to be dangerous...