Requisitions are splitting when requisition lines are returned or rejected by Buyer

We are noticing that when requisitions with multiple requisition lines are created, once approved, they generate single purchase orders if the criteria are met to group requisition lines. However, we are experiencing an issue where, after the requisition is routed for approval and buyers either reject certain lines or return requisition lines for correction, once the requisition gets re-submitted by the requester, some of the lines that were corrected are splitting into different POs.

We noticed that sometimes when the requisition lines are rejected and returned, a different buyer may be assigned to that requisition line, different from the others. However, we were under the impression that the buyer assigned to the first requisition line would take precedence and the same buyer would be assigned to all requisition lines.