More thoughts. Since it stops at the bottom of the opening, and seems to drain to that level relatively fast, my guess is either the pipe or the pipe attachment point at the skimmer bottom. Reason...as the water level approaches the leak level the leak rate slows because the water pressure due to depth drops. This seems to keep going until water doesn't flow into the skimmer and the pipe is still at some depth therefore I suspect the leak is lower than where the water level stops dropping. Make sense? Hope I explained it. Once the water stops flowing into the skimmer does the water already in the skimmer continue to drop? If you can inject dye at the bottom of the skimmer that should prove it.
Al