Weldment BOM does not update properly

This is an issue I have been annoyed by for a long time.

The Weldment Cut list does not update properly. I do not know what or why this happens but it is a big issue.

I have clicked the update button in the model tree view.

I have checked on all the properties of all the weldment parts in the model, they are all set right.

None of the weldment parts are merged.

I have tried to delete and re-create the weldment cut list in the drawing.

I tried to update with the traffic light and ctrl+q.

I tried saving, closing, re-opening, updating, etc...

I tried to exlude from BOM and then include to BOM again.

I hope someone can tell me what is going wrong or what I can do from this point on.

I use SW2012 SP1.0 - hotfix #635912