Backorder Lines are Consolidating

I processed an Invoice with two backorder lines for the same product with the same rate but the discount is different:

If I select Fill backorders and then click Process, the Invoice is created with two separate lines as expected.

If I select Fill backorders and either untick this backorder, or select Exit, the backorder now displays 21 on backorder.

Solution

Infusion will combine the quantities if filling the backorder process is halted. 

There is a warning to have a backup prior to proceeding for this reason.

 

After the process is halted the backorder is combined.

There is a ticket raised to fix this issue #13410