You do have the scale in the middle of the unit where you can see the read out through the opening at the top and with one roller on each side, correct. Not meant to sound bad, I just know that others have done that, so please no offense meant at all....
Try looking at this link - might be that the head is not level and throwing your pressure off. That is one reason it is recommended that the head pressure is checked after shipping.
http://www.carvewright.com/2010CWweb...level_head.pdf