Ekanban creating Internal Requisitions instead of PO

We have seen an issue, when we replenish a card with supply status- Full, and whenever the request set which has 3 child programs under it-
1. Consolidate replenishment
2. Requisition Import
3. Create Internal Order
run, occasionally we see Internal requisitions getting created instead of PO. When we run the request set manually, the issue doesn't occur. It happens only for the scheduled program. The 'Source type' is set as 'Supplier' for the Item.

1.What could be the reason?
2.What triggers creations of Internal Requisitions ?