WO-K-B allows you to edit BOM's on workorders. That way you can add in any parts that are missing.  The question is are the items not being allocated to the W/O, or is it just that they are not being printed?  I assume the former, which is not good.

I know that Lynn and crew have been working diligently to try to minimize the adverse effects of record locks.  Hopefully this is one that can be made better.  
My company is very small and we normally only have one person in workorders at a time, so it hasn't been problem for us. Back a few years ago when we had our peer to peer server an the accounting computer (definitely not a very bright thing to do), we had all kinds of bad things happen due to record locks.