Car seat is loose

I need help on this. My area doesn’t offer the thing where you take it to a fire station or anything unless it’s scheduled months in advance. Anyways, my sons car seat is loose or something. I can reach my arm back and tilt his car seat all most all the way over. It has 3 anchors and the seatbelt is going through it like the instructions say. The anchors are pulled as tight as possible. I have a van and I’ve tried it in all 5 back seats. It’s the same.

Update: I took out the seatbelt and now am using just the 3 anchors. It’s still doing the same thing, it’s very wobbly and can be tilted easily.