Unable to update Item Number from UI on Assets created from Fusion Order Management

Hi Team,

I am not able to update Item number from UI on assets created from Fusion Order Management. However, if I create assets directly in ALM, I am able to update Item number on assets.

Business Requirement:
As part of migration activity, Fusion Orders are being created with Old items which had UOM as Year. Once these orders are processed in ALM via Orchestration, assets will be created with UOM as Year.

However, going forward business want to use new Items with UOM as Each (and eventually deprecate old items).

But, business wants to use same assets which are created for migrated orders. Hence, requirement came to update item number on existing assets to use new Items with UOM Each by replacing items with UOM Year in ALM.