In the map bm_c2a5a, the first map of surface tension, the zoomed view through the crossbow scope is causing some issues with the skybox.
Basically the sky moves a bit with the view:
Founded in 2004, Leakfree.org became one of the first online communities dedicated to Valve’s Source engine development. It is more famously known for the formation of Black Mesa: Source under the 'Leakfree Modification Team' handle in September 2004.
