PS 12.2.5 Demand Pegging

Hi all

We make use of the published Demand Pegging file to link demand and supply loaded in to PS for specific solved scenarios.  I have an issue where for particular items the demand is simply pegged to the starting inventory of an item, despite there not being enough starting inventory to fulfill all the demand and there being supply in the form of work orders.  I have a theory as to why PS is doing this but wanted to check if anyone else experiences the same issue?  I can elaborate more if necessary but I don't want to give too much