Hi Hazem,
Yes we also found that in debug. When the FM is called from SRM KBLPOS = Space where as when posting GR directly in ECC KBLPOS = '000'. In the upgraded system the field value in MSEG is already '000'. Check the snap shot attached.
If you see the comments in FM at Line 79 it talks about a switch FMRE_INV_CONSUMPTION. If this switch is activated the validation will not be done and this switch does not exists in previous version but what other things this switch will affect we are not sure.
Waiting for response from SAP. Do let me know if you find any more information.
Thanks,
Anubhav