[Solved] Mitsubishi PM75CL1A120 - how to decode lot codes S14BH5G and SO3BH4G?

Hi all,
I'm working on railway inverter maintenance and I'm trying to decode the lot codes on Mitsubishi Electric PM75CL1A120 IPM modules.
I have three units with the following codes printed on the label:
S14BH5G (two working units)
SO3BH4G (one failed unit)
I cannot find any official Mitsubishi Electric documentation explaining the lot code format for their power semiconductor modules.
Does anyone know how to decode these codes? Specifically:
What does each character/group represent?
Does it encode the manufacturing date?
What does the leading S (or SO) mean?
Any help or pointer to official documentation would be greatly appreciated.
Thanks

The user provided the data sheet from Mitsubishi