So both you guys think this a just a calibration issue? I'm not saying you're wrong, just that I don't see it that way. From what I can tell this transmission is (in some ways) similar to the 16 X 16 transmission Ford used in some of their early powershift forty series tractors. Four speeds in low range and the same four speeds over again in high range.
What I read in the problem description is that all is well in low range (tractor operates in one through four) but when the demand comes to shift from four to five the system should then drop the low range clutch, pick up the high range clutch, go back to gear one, and thus be in gear five. This isn't happening for some reason. The low to high shift isn't taking place. Is that a calibration issue? Not in my mind. In my understanding calibration (basically) adjusts the speed at which clutch packs engage and disengage based on factors of engine speed, ground speed, gear selection and whatever other parameters the engineers chose to include. Maybe someone can help me understand how that's what this problem is.