When you will do the inspection of FWD vertical pressure bulkhead in MWW B STA 663, focus on web between LBL 40 and LBL 45,64 – it is inboard of speedbrake CTRL cables enter to the MWW. You can find crack along chem-milled area as wieved on the pictures. On first picture you can clearly see that the web around crack going to be splitted. Related to B738, FC 14-15000 , FH 37-41000. Check FTD 737NG-FTD-57-09002 for more info. Thanks to Josef, Czech Republic.