I think I've figured out why there is a lap data issue for many of us with Charge 6 and the iOS app.
In my case, it will display data for a brisk walk as:
Lap 1 9'09" / mi 1.61 mi
Lap 2 9'27" / mi 1.61 mi
...
We all know that 1.609 km equals a mile. So it appears to me that Fitbit is capturing the time required to complete a lap correctly, but is mixing a kilometer value against a mile reference. Thus it calculates incorrectly.
This shouldn't be a hard fix to implement.
