I have no problem with the child seat even if I go over a bump or stop quickly.
I am using this Britax Romer Max-Way Plus | ▤ Full Specifications child seat in my 4runner and it works well. No problem at all also my friend has the same and never face such issue ever.
Sometimes you are posting the same thing that is already posted by another users and cause this problem. You need to search it first to see if the other thread is already sharing this information.