F-39 Clear a customer down payment - F5005: "No down payments exist"

Dear experts,

I'm trying to clear a customer down payment with transaction F-39 but I'm always getting error message F5 005 "No down payments exist" even though I have created down payments.

I've created the billing document FAZ, I've posted the incoming payment with F-29, I've create the billing document F2 (for the whole amount) and now I wanted to clear the down payment but I'm always getting the message F5005.

I already checked the SAP note 1422743 but we haven't implemented any EHP, so it doesn't apply to our system.

Any idea what I might be doing wrong?

Thanks in advanced