Facing the error while unassiging the assigning the deliveries

 hi,i am using the wsh_delivery_details_pub.detail_to_delivery for assigning and unassigning for deliveries 

while unassining is happening correctly and after unassigining i need to again assign the delivery_id

at that time i am getting this error

'Warning: These entities can not be grouped together as their grouping attributes do not match.

Error: Error in assigning one or more details to a delivery.

can any body please suggest how to fix this problem as this is a functional setup

Thanks In advance

Regards

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DRK