Lots of good ideas.

The order I would pursue it is:

1. Make sure the half width gates are open on both tanks

2. Go into the Air Cart page, then the meter setup and verify that the front and rear meters are set properly on spacing and so on

3. Perform another calibration. Count the number of times the meter turns when you do the calibration.

The display will also count the number of turns. Verify the number of turns you counted and the number of turns the monitor counted during the calibration process are equal. I believe following those three steps will get you pointed in the right direction.