I've been out on a steady run twice with my 255 but it has added an extra lap to each run. I run 6.5M with 0.5M laps. The first time laps were recorded OK to 3.5 then at 3.66, 4.16, 4.66, 5.16 etc. to the end. The second run was OK to 3.5 again then at 3.88, 4.38, 4.88, 5.38 etc.to the end. My R hand is nowhere near the watch when it happens so I'm not pressing any buttons. Any thoughts as to what is causing this?