We have this strange occurrence with our average cost and wondered what might be causing it.  It only happens occasionally and we can't figure why.
 
When materials are issued upon shipment of the job, I'll check JC-E (Material Issues) and an item will have issued for $0, but with the correct qty.  Then if you pull up the inventory item, there will be no average cost.  I've also checked the previous issues for this item and it did issue properly.  
 
It appears that something happens to make the average cost go away.  Does anyone know what would cause that?  
 
Luckily it's a pretty easy fix.  We'd just like to prevent it if possible.

We use Average Costing (per SD-H).