where it doesnt feel like its fully pressurised?

There's definitely liquid in there but theres also plenty of give when i squeeze it. it's not leaking or anything, just a bit suspect. the off licence down the road have a habit of this sort of thing.

I'm not really interested in whether its safe to drink because I'm gonna drink it regardless, but still, not right. Anyone know what I mean? Maybe it's not been filled to capacity, idk.