first off using 3rd party parts isnt always a good thing , always try and use OEM parts if availaible.

when installing the lift pot it is recommended to 'precenter' the pot to 653ohms, then using the below mentioned voltage ranges and having the truck in test mode set it center voltage of the expected ranges, the 653ohm range should have it farily close. Then once set run the learn mode test to calibrate the TMM to it.

secondly if your just testing then try going into the 'analog' test mode and go to test A04 and check the lift/lower pot voltage and see if it is staying within the expected ranges for this circuit which would be 0.156v - 4.84v , anything above or below this reading would trigger this code.

Also i noticed they have a revised OEM part number for the travel and lift pots, unfortunatly the service gram does not specify which one is which , i'm sure the parts person can determine this though when he checks the number
SE000258 and SE000267

the other suggestions for this failure would be:
incorrectly adjusted liftpot
control handle wiring may be faulty
bad carriage wiring board
mast cable (you already suspect this one)
learn mode needs to be run (you already did this also)
control handle may be moving beyond designed parameters due to a mechanical problem
and lastly a bad vehicle manager (lets hope its not this one)

now from the sounds of it you may be in the right area but maybe your testing method for checking the mast cable is not correct? instead of ohming the cable wires try doing a resistance check instead. generally if there is a break in a wire there will be higher resistance that will show up that ohming may not.

Just a thought

good luck