After a while, i reviewed the PCB's and just found the different between the two PCB'S, the UD-1200 and the UD-1200 Pro. It's resistor R41, 2,2 kOhm (222 top marking).
R41 is present at the UD-1200 PCB. The pads are unpopulated on the UD-1200 Pro PCB.
After placing a 2,2 kOhm resistor to the Pro PCB, flashing the UD-1200 firmware, it starts as a UD-1200 with full temperature on T-245 handle. The T-210 handle is not recognized when R41 is soldered.