There are many people do not install the car seat perfectly because of lack of education. It is important to follow the guidelines of the car as well as car seat manuals to properly install the car seat. You must have to see the installation guidelines and locking clips and belt is not properly installing into the system.
You must have to test the child seat one it gets installed. You must consider that the car seat must be pull hard to install. I think the child seat must be rigid.