Issues with Zwift races/group workouts

Hi. New Zwift user here, experiencing some issues during group workouts and races. I use a treadmill, Garmin Fenix 6 watch (with virtual running as activity) and Stryd footpod. I paired my Garmin watch and calibrated it with the 3 steps process for speeds between 10 and 12km/hour. When I run by myself, all is fine. My avatar runs at the calibrated speed. When I join a race, however, my avatar is not moving at all, even though I am running. I then tried joining a group run, and went to the starting line 5 minutes early. Began walking on treadmill (avatar showed blue treadmill underneath feet). With the start signal, I hit the 10km button and started running. Avatar did not move again, pack pulled away, but after a while, my avatar decided to start running. However, he did that at incredible speed, way faster than I was actually running, passing the pack within 30 seconds What am I doing wrong?