[woodcote]

If it's every other lap, I'd check the minimum lap time setting (sometimes known as 'de-bounce') in the software. If it counts when you go slow, that makes sense. There should probably be a noise from the program on the lap when it doesn't count.

If you're running Race Co-ordinator, it's always good to have a copy of the Trackmate software available - then you can check if you have the same problem on both programs. That would suggest a hardware problem (or a too-high minimum lap time on both!). If the issue is just on Race Co-ordinator, that would suggest an incorrect setting or a bug.