Why Min/Max Planning went to create a SPO Requisition even through there was no Consumption Issue?

 We are having some Consignment problem which we can not find an explanation:

Sometimes,  our Consignment Min/Max Planning job went to create a SPO Requisition even through there was no Consumption Issue for some Item. This problem is not happening for some specific Item, Supplier or Sub. It doesn't happen every day or every week. We use Consignment for over 1 year and this problem only happened a few times.

We did the investigation about everything we could think about:  There was no Min/Max change for that Item, no Consumption Issue, no SPO cancellation or Closure, and no SPO Return or Adjustment. Anyway, we just don't know why sometimes the Min/Max Planning job thinks that some Item QOH is below MIn even there was no any Inventory or PO Transactions happend for that Item.