That is really a training and process issue in my opinion. The staff need to understand that moving stock into or out of 916 with a 999 TO does not update the delivery statuses and in the exact same way they need to understand that deleting a delivery does not put the stock back in the source bin. They need to understand the way a pick TO updates a delivery while other TO types do not just as much as they need to understand they should not delete a delivery before adressing the stock.
It is not any more difficult to move stock out of 916 with LT01 after a delivery is deleted then it is to return the stock with LT0G so really the only issue I see is training and basic understanding is needed.
If the staff dont have this understanding you will see issues indefinetly with people moving stock into and out of 916 thinking it will update the delivery (when we know very well it does not).
Just my thoughts on your question - sorry to not give you a specific solution for your error message
I can recomend that you set the TO confirmation to immediate when using LT0G - theres no point in having them use LT12 to confirm.