refund / invoice / Too many reversed items on an invoice

[Florian Reitmeir <..hidden..>]

Hi,

we tried to make an "refund" invoice. 

In detail we delivered some goods, and now some of them came back. In
such a case we normally generate an invoice with negative quantity of
the goods.


In this case, every line has an negative quantity and value.
And the invoice is printing fine.

But we can't book it. If we try we get an error:
   Too many reversed items on an invoice
 
Any explantion? How can a refund fail if we get our products back?

--
Florian Reitmeir