Zend certified PHP/Magento developer

Custom attribute shipping address update to null after invoice or shipment

I have a plugin with multiple functionalities and one of them is to add a custom attribute on address and on checkout I am updating the attribute value via AJAX with on click javascript. The value is in DB and also after order is placed is moved correctly from quote to order table, but when I am invoicing the order or doing a shipment, the attribute value is NULL. Based on debug, this value is not from my code as I’ve alter the code and add different values instead of NULL to check.

What can be the reason for this?