Actual ship date is blank for Sales order

Hi Team,

User has selected an parent kit item as SO line 1 and kit component as  SO line 2. During shipment approval process, he is supposed to select only the parent kit item line 1, in this way it works well where ACtual ship date is updated and also Location/Lot updated correctly to Kit component line 2.

Not sure what happened for one particular order, Actual ship date is not updated neither in Parent Kit nor Kit component line but somehow order is ready for shipment confirmation.

Also,i could see the Sales update error as - "Invoice has not processed"

Please suggest