Air Pocket in RODI

[Mrmiles]

The final RODI stage of my RO unit has an air pocket in it. The water level never completely fills to the top and fluctuates slightly. It was pretty low before so I changed out all my cartridges. Its still happening. 65PSI going in.
What's the possible issue?

 

[Mrmiles]

 

[homer1475]

Trapped air, it will eventually work it's way out. Or just unscrew the canister slightly to let the air out.