Not a seat rail failure injury but clamp based injury.
I have a friend in his fifties who as a young lad was riding behind a friend when his seat suddenly tilted back, screamed as he skidded to halt and crashed still screaming.
When going to his friends aid it became apparent that the boys tackle had become jammed between the seat stays and rear wheel forcing the skid and subsequent crash.
And the boy was left in heap still with his bits well and truly wedged, screaming such a scream my friend had not heard before or since.
After a attempt to free the boy by brute force failed spectacularly he let the air out of the tyre and gently backed up the wheel finally releasing his friend, who instantly jumped to his feet and ran home at fast as he could clutching his jewels still screaming ferociously .
When ever my friend tells this story he is in absolute hysterics with tears streaming down his face.
In sympathy I am sure.