Hi, Christophe,
Regarding the difference between date code 1628 and 1843, frankly speaking, I do not know.
If you use CodeWarrior for DSP56800E ver8.3 or CodeWarrior for MCU ver11.x to download code to flash, is the MC56F8355 okay or not?
If the MC56F8355 for date code 1843 can not work with the CW tools, I suppose that the FAE has to be involved and failure analysis is required.
BR
XiangJun Rong