Did you create the delivery against a Stock Transfer Reservation, and post the delivery?
If you do so, please check that the stock transfer reservation is new and you didn´t do any delivery posting (with mov. 541) against it. I mean, suppose that your stock transfer reservation has 10 UN. If you first do a 541 against that transfer reservation, let's say for 4 UN, create the delivery and post it, and then you do a 30A against the same reservation,then you can create the delivery and post it without dump, becausae the field ENMNG was updated when posting the delivery with the first movement 541, so it´s not equal to 0.
However, if you have a completely new stock transfer reservation, and you create a movement 30A, and then you create the delivery, you will get a dump when posting the delivery because the field ENMNG didn´t get updated (it´s equal to 0). That´s why it was hard for me to reproduce the error.
I mean, the delivery created with 30A is not able to update the field ENMNG of the reservation, hence the dump.