VF04, problem during massive processing

Hi all,

we have a problem running transaction VF04 in massive mode, some times the invoices are registered without respecting the sequence of deliveries processed, so the date into the invoices created are wrong and not correctly sorted.

I guess the problem is generated by the processing mode of VF04, synchronous or asynchronous, we are running transaction in asynchronous mode, is it possible? Or have I looking for any old user-exit?

Thanks GN.