This is a mild incident, but is perhaps worth sharing. A person I am very familiar with was learning to climb SRT. The rope was set up high in a union, and the base anchor was set. All looked right in front and behind. At about the 25' mark the person noticed that the rope on the other side of the union wasn't hugging the stem as expected. A few more feet up and the climber saw that the rope extended around a dead and skinny branch before attaching to the base. A quick estimate suggested that the climber would drop more than safety allowed, so the climber descended. The branch broke when the climber was 6' from the ground. He landed flat on his back, only suffering a mild concussion and damaged pride.
This could have been much worse of course, and the climber learned a valuable lesson.
This could have been much worse of course, and the climber learned a valuable lesson.