we have faced the same issue, it is very practical, if you have not taken credit or captured in Next GRN, you can change the status to "P" forcefully in table j_1iexchdr or through Z program then the In process documents status become Posted. it will appear in J2i8 for transfer too.
Regards
Maruthi S
Scenario more or less same.
Done the GRN, Par II posted
Cancelled the GRN without cancelling Part2
Invoice Status became blank that is in process
done the GRN again by selecting No excise entries.
Regards
Maruthi S