Help!! Car seat advice or recommendations!


I need some advice! My husband and I bought a new car seat for our 8 month old and we cannot get the seat to stay still! It moves all over the place. We’ve even bought a car seat grip and that didn’t help at all. We took it to the fire station and when we left we realized it was sitting uneven on the seat and once we got home it could easily move more than an inch to each side. I couldn’t believe it! I’m not sure if it’s because my middle back seat is smaller than my others or what. (See the picture below.) It worked perfectly for my previous car seat with a base though. My middle back doesn’t have latch so we are using the seat belt but the shoulder belt almost seems like it’s holding it up....please help! I don’t want to return the car seat but I refuse to put my son in something unsafe. If anyone else has had this problem how did you solve it? Or what car seats have you all not had this problem with and we’re able to use the back seat with the seat belt. I drive a 2007 Ford Edge and the car seat is a 3 in 1 Everfit safety 1st.