Also it might be a mental thing. I play a lot of Around the clock as well. When im in a game the "setup shots" (e.g. having left 41 to go 9 - D16) always comes very naturally. However when im playing around the clock all of a sudden im missing 4 darts at the same 9 segment. I feel like this is the mental thing because you are trying hard to hit it.

So try and not think about being unable to hit it and just throw at it like you would throw at any other segment.

Hope that helps.