The total wip Using wip summary or materials in wip is not correct.  The value for assemblies are added to wip as well as the components in the assemblies.  This will double the wip value.  
Example: An assembly has two components at a cost of $50.00 ea. There are no additional costs for the assembly.  The wip value should be $100.00.  But the top assembly puts $100.00 in wip and the sub assembly parts add an additional $100.00 for a total $200.00.
Am I doing something wrong or do I need to forget wip and backflush at final production.
 
Dan

IS Tech introduced a new report last December - JC-R Print Multi Level Assembly Cost that addresses that very issue.  It is similar to JC-M but only type M and R components are included in the Material Column.  It is still potentially inaccurate because a type M may contain a subassembly but it was the best we could do with the existing data and is certainly better than what was originally there.
 
As for the original post, sounds like the subassemblies are being issued to the assembly work order before you are doing WO-I for the subassembly work order.  Have to make the subassemblies before you issue them.