NAS misses items sometimes

Hello

One of our customer exports items with an XML-port. The Customer has LS Retail and the LS Retail Sceduler is used together with the NAS to run a Codeunit that runs the XML-port. The XML-port filters which items to include in the export and exports them. It happens occasionally that items that should have been included is missing. This probably happens once or twice per month. On these occasions I have run the job manually through Functions -> Order Job of Scheduler Job on the LS Scheduler Form and all items have been included in the file. As far as I know that function is just a way to tell the NAS to run the job as soon as it can. So it should work the same way. Does anybody have any idea why it misses items occasionally when run automatically but works every time when run manually?

Thanks in advance