amount to draw from down payment is not set in document currency

hi,

i always get the error "amount to draw from down payment is not set in document currency" when i try to update a draft of invoice with down payment.

i do the following:

1. sales order

2. down payment

3. income payment

4. delivery note

5. invoice

5.1 save as draft by di api

5.2 get draft by key

5.3 do some changes, for example change comments by di api

5.4 update draft by diapi <--- the error is thrown!

If i do this on screen everything works fine. But by sdk its not working.

System: SAP 8.8 SP00 PL20

Is there a solution for this problem?

best regards

Markus