When the summary Quantity on Sales Order or Quantity on Purchase Order does not match the order details, you have to rebuild the sort files.  This is a Library Master Utility ran after hours.  I recommend doing PM First, if applicable, followed by PO, SO next and Inventory Last.  Sage has a knowledgebase article here:  https://us-kb.sage.com/portal/app/portlets/results/viewsolution.jsp?solutionid=222924250017929&page=1&position=1&q=rebuild%20sort%20files 

Thank you, we had sort files rebuild and it corrected the problem.   Any reason this happen to being with?  Maybe something we can do differently next time.

Thanks again for your help.

Rebuilding the sorts should be part of your normal month end close routine. If you have heavy volume then I would suggest once a week. Nothing you can do different to prevent.