Unable to create Revision after shipping the lines if there is a carrier updated in the shipment

When we try to create a revision after the Lines are shipped with a Carrier value updated in the Shipment, we are seeing an error '

The carrier cannot be updated because the fulfillment line was fulfilled. Source Order Information: {Order Fulfillment line number}

We are not updating any carrier information here but trying to update the header EFF. Why are we getting this error?

When we try to update the header EFF when the carrier is blank in the shipments, there is no issue seen.

Please help.

Regards,

Karishma