Yesterday i found finaly the T-MST4DEUC engineer 0000 firmware, tested it on my ue40d5000 and you can downgrade directly from usb to lower version.
T-MST4DEUC-0000http://www.devil-strike.com/samsung/T-M ... 0000.0.rar
(dont use this as standard firmware you will see NOT FOR SALE if you press p+/p- in normale mode).Be aware after installing the 0000.0 firmware your tv will reset everything, you also must reset eeprom from servicemenu(via ruSamsungTVCommunicator to extend service menu options) if you dont reset eeprom you cannot set model in service menu(you will only see Error in model screen) after eeprom reset you can select your model, localset enz.
Firmwares after downgrade:
T-MST4DEUC-1024.1http://www.devil-strike.com/samsung/T-M ... 1024.1.rar
T-MST4DEUC-1025.0http://www.devil-strike.com/samsung/T-M ... 1025.0.rar
All Those Firmwares are tested and working on a ue40d5000 ci+ with T-MST4DEUC soc.
Downgrade 1027 to 0000
Installed 0000 Firmware
Upgrade 0000 to 1024.1 Firmware