How fast are you trying to print? Does it behave differently if you slow down?
One of the reasons prints can shrink like this is that the speed is essentially stretching the plastic as it comes out the nozzle, like a rubber band. As the plastic settles that tension pulls it together.
I doubt moisture is the issue, PLA doesn’t actually absorb water very quickly.
Also, have you done a temperature tower and flow calibrarion for this filament?