Requirement Type on Sales Order didnt follow assignment logic

We had 2 sales orders that had the requirement type incorrect for the material on the procurement tab of the order. Our system sets the requirement type based on the item category. These sales orders then kicked out special stock POs due to the type of item category assigned to the material. Due to having the incorrect requirement type from the sales order lead the GL account assignment to be incorrect on the PO and the items not being able to be received in correctly. We were able to get a work around for this but want to understand how this could have happened.

Our configuration for item category, requirements type and requirements classes are correct and this seems to be a isolated incident as we had been moving right along with no issue and got 2 of them in a weeks time and haven't had it happen since. I cannot replicate the issue in our test environment as any change made to the material's item category is updating the requirement type to the correct value.

I can get the special stock PO to assign the incorrect GL account only if I manually change the requirement type in the sales order which is the only way I can get the requirement type to be incorrect and did also confirm with the sales order creator that they did not update that field in the procurement tab manually.

Has anyone seen where the requirement type didn't update/redetermine on a change to a material or item category in the sales order or have the requirement type not follow the configuration set forth in SAP?