The case happened recently in one of the indoor climbing walls in Prague and thankfully nobody was injured because the fall was just above the first quickdraw and the falling climber landed OK.
The rope was reported as a brand new (two weeks old)from a well known manufacturer.
After the case the report was published and the climbing public was warned of the risk.
The wear on the carabiner was probably because the intensity of the rope friction there is enormous. Logic says that it could impact the last carabiner on the route (which does not catch falls), and according to this new incident the first one as well- where the fall factor is the most critical.
Picture 1
During lowering the rope enters the carabiner in a specific angle and at the upper edge of the carabiner the rope further sharpens the body of the carabiner to a flat surface and a sharp edge is formed: Picture 2 below in the text.
The description of the incident: The fall of the first climber from the first go on protection, the rope was cut through, the climber fell to the ground, luckily without any injury. The length of the fall was 1,6 m. The fall factor 0,57.
The mass of the falling climber was 80 kg. Belayed statically. The rope was single dynamic 11 mm diameter.
Picture 2 and 3
The carabiner long term used on the position of the route first protection.
Picture 4 a 5
The rope cut off in the incident
Picture 6 a 7
Detail of the cut rope
Conclusion: Climbing wall providers should regularly check the carabiners and those showing significant wear in the rope basket should be replaced by new ones. Higher attention should be placed on the first ones on a route or the others which are the first in the direction of the rope (e.g. under overhangs, in the beginning or end of traverses etc.).
In case the visitor of the climbing wall would find any grooved carabiner, he/she should notice the climbing wall provider.
Source in Czech:
www.horosvaz.cz
Registration
lezec.cz
The safety commission of the Czech Mountaineering Union recently reported an incident which involved a falling climbers rope being cut completely over the edge of a well worn carabiner. 
