Hi Wayne,

i tried to repeat issue, but i couldn't. It was able to create invoice. I tested with steps:
1. Created new Sales order
2. In header Order Type = Normal
In matrix row Order Type = Drop Ship
3. From Sales order > Created new Purchase order
4. From Purchase order > Created Shipment notification
5. OK Shipment notification
Result: Del. & Del OK is updated on Sales order

I have same result if on Sales order header Order Type = Drop Ship