Purchase Orders - Subcontracting wrong movement type 545

First of all this is not about asking a clarification of what is MVT 545 or MVT 543

I'm asking why the system is behaving in this way however there is no BOM for the material or even negative indicator

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Dears ,

We are facing a problem regarding subcontracting purchase orders , as for the same Material & same Vendor , some times while we are receiving purchase orders the MVT 545 shows up instead of 543 , This happen automatically and we ca not change it , However for other purchase orders for the same Material & Vendor it shows up MVT 543 which is ok for us

We need to make sure that the MVT is 543 while we are reviving , So could you please clarify the reason of this system wrong behavior

Note : our purchase orders are a reference to a PM order

The problem is that we didn't create any BOM for this material , and the second thing that some POs for the same material work fine and posts with MVT 543 not with 545