Hi Dushyant,
As far as I understand, you have different address for Plant and Storage Location hence you have defined separate Legal Unit for each.
But now in this case, you have not defiled legal unit for Plant/Storage location combination but still system is picking legal unit corresponding to plant and carrying out the checks which is expected behaviour as per standard.
To avoid this situation, I believe you should only define a Legal Unit for Plant/Storage Locarion combination. In this case, legal unit mapping is not required for plant alone.Hence, if you have not created a legal unit for plant/storage location combination, system will not find any legal unit and block the document.
Regards,
Kul Vaibhav