Invoice on status not working

[StSt]

Hello,

We got quite a problem with our prestashop v1.6.1.0, regarding invoices:

 

When we set our orders to "In treatment" and want to generate invoices on that specific status, we just get a few invoices, but not all of them. So we got 11 orders (ID 329 to 339) which are currently set to In treatment, but we can generate just 3 invoices (ID 329, 338 and 339) by that status, 8 are missing. 2 out of those 3 which show up are bank transfers, 1 is a cash on pickup.
 

Knowing that it seems like an order with cash on pickup payment can generate an invoice, but it seems that all the orders, also earlier delivered ones, which were paid by cash on pickup - since we updated prestashop (and the cash on pickup module) to 1.6 a few weeks ago - don't generate an invoice. Except for that single one mentioned above.

 

We got three carriers which are actually all pickup places, but I guess it has to deal with the cash on pickup payment. The missing 8 orders have all cash on pickup payment.
Out of the same 8 orders I can create an invoice one by one out of the invoice-icon in the orders list, but in those invoices the total price is set to zero(!?). The invoice number of a single invoice then allways starts with IN000000 and there is no invoice showing up at the documents tab on the details page. The 3 invoices which dó work don't have these issues.

 

We would really appreciate any help, since this is a major bug for us, we have to deal with the invoices every week.

 

StSt

Edited August 27, 2015 by StSt (see edit history)