NAV 2013 Report Problem same picture on 2 print

Hi everybody,
I have a problem with pictures in my report RTC. On each print of the sales invoice, I display a picture in header. This picture depends of the invoice.
If i print sales invoice one by one, no problem, the good picture appears.
But if i try to print 2 sales invoice (select 2 lines in page "Posted Sales Invoices" and click Print button ), it's the same picture on my 2 sales invoice.

Do you have an idea please ?

Thanks