There is an issue with the microsecond calculation in getDateTime in _GXCommon.py (at least in the python implementation).
The ms are correctly computed, though they are treated like HOS instead of ms. Please find a fixed version attached. It only has a couple of modifications:
line 589: ms > 100 is replaced with ms >= 1000 -> I assume that 1000 is an invalid value...
line 599 & 601. ms are multiplied by 1000 since datetime input is in microseconds, not ms.