Does it happen? You bet. But is it normal? No. However most zoom lenses of this type will creep sooner or later if you use it a lot.
Depending on how old it is, you may get Canon warranty to service it. They can tighten it up. My 24-105mm f4 L does that too.
I just live with it as this lens has seen a lot of duty.
This is actually a pretty nice lens. I was thoroughly impressed with the one I got to try.
Check out Lens Bands here: http://www.bhphotovideo.com/c/search?Ntt=lens+bands&N=0&InitialSearch=yes&sts=ma
They should solve the problem for you. They also make good camoflage for the red rings on L lenses when I don't want to advertise what I'm carrying.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
04/20/2023: New firmware version 1.4.1 is available for EOS R3
03/30/2023: New firmware updates are available.
2/07/2023: New product announcements!EOS R8 EOS R50RF-S55-210mm F5-7.1 IS STMRF24-50mm F4.5-6.3 IS STMRF15-30mm F4.5-6.3 IS STM