Zwift running - Inaccurate speed

Hi,
I tested this morning Zwift for runner. It’s seems promising but the most important feature, running speed, is inacurate.
I’m using a Garming FootPod bought in 2012 (model:01397) and the speed of my treadmill (and my speed feeling) is constantly faster than what the pod report.
For example, 8kph is reported as 5kph, 10kph as 6kph and 15kph as 10kph. This is quite annoying.
Would anyone have noticed the same thing?
Fred

I’ve noticed that too, but not as extreme.

I have a brand new Garmin footpod, and prior to callibrating it, both my Garmin watch and Zwift were reporting the exact same speed.

My treadmill was considerably slower.

I then callibrated my watch to match the treadmill speeds, and got it within 2-4s per kilometer.

Zwift is still showing the original speed, which is now about 15-25s faster per km.

Must not honor my callibration setting…