"Send in Bulk" and recipient/signer indexing in the CSV file

Case description:
I want to use the "Send in Bulk" feature in Adobe Sign to import a CSV file with data, automatically populate a document, and send it to 4 signing parties.
For this purpose, I created a document template containing text fields named identically to the column headers in the CSV (e.g., "StudentFullName"), and signature fields for 4 signers are defined on the last page (in no particular order). Each line in CSV contains 4 recipients/signers and "Merge data" to populate the document.

My issue:
The CSV data import process completes successfully, but only the first signer is imported—the remaining signers are not. All other data is correctly imported and populated into the document.
I suspect the issue lies in the CSV file, specifically in the header indexing for the individual signers, as the original CSV template from Adobe does not include indexing. As a result, it is unclear how the indexing in the CSV should be formatted or defined so that the process correctly identifies the additional recipients/signers for whom signature fields have been created in the document.

Is there a solution for this?

Thank You

Rs.