Storage Location determination in return sales order

Hi SD Gurus,

While creating return sales order with reference to a billing document, sales order is catching wrong storage location.

I had checked all the assignments in "Assign picking location" tab. No problem there.

Rule - MALA.

My question is

1) Storage location determination takes place @ delivery level. Why this determination is taking place @ order level?

2) Why its catching wrong storage location?

Please help.

Regards,

Balaji Parsewar