Different Pricing Schema in PO and PIR for same vendor and material

Dear Experts,

I am facing an issue related to MM.

I have a vendor and a material under a plant, purchase Org, purchase group.

When we are creating a Purchase Info Record (PIR), it is picking one pricing schema, while when creating PO for same vendor and material, it is picking another different pricing schema.

As per my knowledge, pricing schema in PO is picked as per pricing schema group of Vendor and I believe same applies for PIR as well. I have only one vendor pricing schema group.

Because of this issue, I have to manually key-in condition values in PO for all condition types even though I have maintained a purchase info record.

Please suggest, what can be reason.

Regards,

Praveen