Inbound Shipment Line screen does not allow edits

Symptom

On screen YOMD7342 - Shipment Line Details - there is a list of Tag/Serial numbers. I can not delete or change the value of the tag/serial number.

This is for inbound shipments when the shipment is in shipped status. The delete button does not do anything and when I change the tag/serial number I get an error message.

YDM00120 : ShipmentLine quantity cannot be less than sum of tagged quantity of the line and containerized quantity
[ShipmentSubLineNo : 0, ShipmentLineNo : 1, ContainerDetails Quantity : 0.0, Tagged Quantity : 2.0, ShipmentLine OverShipQuantity : 0.0, ShipmentLine Quantity : 1.0, ErrorUniqueExceptionId : 10.72.31.4712835262587200000000001024, ApiName : changeShipment, ElementCount : 1, ErrorUniqueExceptionId : 10.72.31.4712835262588640000000001025, UserId : 625339, ProgId : Console] com.yantra.yfc.util.YFCException at com.yantra.ydm.business.YDMChangeShipmentImpl.doValidations(YDMChangeShipmentImp l.java:3957) at com.yantra.ydm.business.YDMChangeShipmentImpl.updateShipment(YDMChangeShipmentIm pl.java:2940) at com.yantra.ydm.business.YDMChangeShipmentImpl.handleChanges(YDMChangeShipmentImp l.java:1904) at com.yantra.ydm.business.YDMChangeShipmentImpl.changeShipment(YDMChangeShipmentIm pl.java:339) at com.yantra.ydm.business.YDMChangeShipmentImpl.changeShipment(YDMChangeShipmentIm pl.java:261) at com.yantra.ydm.business.YDMChangeShipmentImpl.changeShipment(YDMChangeShipmentIm pl.java:256) at com.yantra.ydm.api.YDMApiImpl.changeShipment(YDMApiImpl.java:907) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.jav a:25) at java.lang.reflect.Method.invoke(Method.java:597) at com.yantra.interop.services.api.ApiHelper.invoke(ApiHelper.java:540) at com.yantra.integration.adapter.DefaultIntegrationFlow.invoke(DefaultIntegrationF low.java:191) at com.yantra.integration.adapter.DefaultIntegrationFlow.invoke(DefaultIntegrationF low.java:91) at com.yantra.interop.services.api.ApiRequestDispatcher.invoke(ApiRequestDispatcher .java:79) at com.yantra.ycp.api.YCPMultiApiImpl.multiApi(YCPMultiApiImpl.java:159) at com.yantra.ycp.api.YCPApiImpl.multiApi(YCPApiImpl.java:2080) at