Guessing, since I’m no pro at GPS units, but maybe the release of microcode in your friends Mychron is out of date or different from yours.
When your friend downloaded his session with the GPS unit, did it have one lap time for the entire session or was there zero time for the whole session. If there was a total session time, that can be broken down into lap times. This link to the AMI Insert Lap Video might help. https://www.youtube.com/watch?v=cTc-FumI2kQ
LAD Specialties / tony kart / rotax / kt100