I would guess there were/are many incidences of injury or worse caused by spent ordnance. I well remember watching a Spitfire chasing a German fighter at low level and firing, no doubt in desperation, out of range. We watched his tracers lazily curl into the roof of a bungalow some distance from us. We hiked over there to find some 5 or 6 rounds had made quite a mess of the tiled roof.
One night a 40mm? Bofors shell fell in the road near us and I was horrified to see that a piece of shrapnel had gone clean through a wooden fence paling which was about half an inch thick.
Such incidents were doubtless repeated thousands of times.