We find out that default warehouse can't work well in sales order. Especially generating BOM. Pls give advice
You are correct that if a user has a defualt warehouse assigned by way of user defaults, the system does not recognise this as a "change" to the warehouse when adding an item which is a BOM item, therefore the components and the item are issued from the default warehouse associated with the BOM.
I have logged this on the product development forum as an issue already, but more weight would be appreciated.
The workaround from SAP is to allow all users to change the warehouse, which is not workable from a security viewpoint either - you don't want junior staff able to transact other warehouses.
The only viable workaround I see is to create a BOM for each item form each warehouse and only have those items available in one warehouse, which does create a huge volume of additional items, or to create a UI add on which automatically changes the warehouse in the docuemnt to the warehouse belonging to the user...