This is in P3Dv5.1HF1: The yellow center line surface marking on Taxi L between SS and Z disappears in front of the aircraft as the aircraft moves along at normal taxi speeds (15-20 kts). Further ahead it is visible and from other views there isn't a problem. All display sliders except water effects are full right, AA is set to 2xSSAA, no FXAA, texture 4096, dynamic streaming off. Minor annoyance but very unusual, thought I'd mention it.