The cybex car seat on the mamas and papas flip xt2 does the same. I think its because its a different make car seat to base and on adaptors. We rarely put the car seat on the base as babies aren't supposed to be in car seats too long.
We have it, no baby here yet but ours does move a bit. Not enough to think it isn’t on but it has a wiggle to it.
I have the same set up as you and ours moves a tad too! I think it’s down to the adapters!
Yeah we have it and you just need to make sure it’s clipped in properly took us a couple of times to get it to feel more sturdy
I have an ickle bubba stomp and mine does the same thing I thought it was down to going over different terrain! X