I copied this from our quality bullitens from work, which are where the a/c crew report any issuse they have witht he aircraft.
Captain unable to re-enter flight deck
Just before top of descent captain went to visit the toilet. On attempting to access flight deck, despite normal use of entry procedures, he was unable to open the flight deck door. During flight SCCM had noted door was quite difficult to open and had raised a cabin tech log entry. Captain made repeated attempts to access flight deck using normal and emergency procedures. Eventually co-pilot had to unstrap and momentarily leave the controls to open the door. Flight deck door remained closed for remainder of flight. Defect raised in aircraft log.
this one made me chuckle till you realise how serious this could be!!!