According to your description, 6400em is Modbus slave and you are using a Modbus-profibus coverter connect to CI854. We have done a lot with schnieder EMs using CI853 with modbus communication, which means the EM is probably all right. And the converter is from professional vendor it quality and function should be all right as well. As I know for CI854 connect 3rd party profibus device, you need to import a GSD file to get the data structure. And the converter should need a configuration to mapping modbus register to profibus data. So is there any chance that the mapping has some configuration error? As I experienced some of the vender provide the modbus device with address 0-based and some are 1-based, which may result a misordered data table.