P31410 not picking up frozen cost on some items from one B/P

When we attach the parts list to work orders for some items at one of our B/Ps the frozen cost is not getting picked up for the parent and is throwing it all into the engineering variance. The only thing the items have in common is that they all have the same G/L class code but it doesn't happen to all items with this class code. It was working just fine until the end of last month (March) and I don't know of any changes that were made.

I think I have covered all the triggers for this to work properly. Does anyone have a suggestion for something I might have missed?