Right, thanks Dommie. Would that be in the UK as a short version was on here a few days ago.
Turns out they were returning for a search & rescue mission in a beat up wreck of a plane that had been rebuilt and wouldn't fly straight and level without a great deal of effort. No wonder they went down.
According to utube videos both the B17 & 29 had mystery flaws that caused the loss of one plane a day, poor devils.
With the B29 it was the engine cooling flaps jamming open and acting as air brakes.