The obvious answer is that the two production units are NOT identical.  If they were identical, then the results would be the same.  I would first question the dimensions of the vessels.  Minor differences in impeller clearance, spacing, or location could account for differences in power requirements.  A difference in amperage could be associated with a difference in voltage going to the motors.  Differences in the motors, manufacturer, windings and even non-standard designs could account for electric current differences.  The description does not say that different amperages are causing operational or process problems, so who cares?
 
Rotating an impeller with parabolic blades in the opposite direction is not advisable as it will substantially change process performance.  It is possible that direction of rotation also would account for the power differences mentioned.

This problem would require a thorough, on-site review of both the process and equipment to make a determination of the cause of the amperage differences.