Unable to transfer bunch of assets to a employee using FA_TRANSFER_PUB.Do_Transfer() submitted via c

I have 2 scenarios where my custom Conc Program (CP)  is behaving differently. I am running my custom conc program on 11.5.10.2

Details are provided below:

Our main goal is to transfer millions of assets currently assigned to NULL/XYZ employee to a new employee 'BBB' and regenerate accounts based on our FA workflow generator for a business change request.

1) Working scenario: I submit my CP which will pull all eligible assets (based on certain conditions) under a particular FA book and transfer to a new employee which I pass in the CP parameter. All assets get transferred in 1 go without any issue if all validations in API succeed.