Same. I had to change the car seat level position to sit him more up, he hated feeling like he was laying on his back. Also, search on YouTube “the happy song” by imogen heap and magically it helps them stop crying. I put it on repeat.
Yea my son just gets really lonely back there and he hates sitting in one place too long
I play the puffin rock theme song on a loop and the crying stops immediately and he falls sleep
We removed the body insert and it gave baby a bit more room, which seemed to help with her posture and comfort. Not sure if you have those in there. Other things that helped —- some toys on her car seat handle, portable sound machine, and practice just sitting in the seat/making short drives etc.