The E-shifter can slip or ‘pop’ slightly when shifting gear – this is completely normal. When shifting from gear 2 to gear 3, there is a half-spin interval while the gears engage. When shifting from gear 3 to gear 4, you may hear a slight popping sound. This is caused by the movement of the E-shifter’s internal mechanism.
If this bothers you, you can apply less force on the pedals at the shifting moments.
If all gears are slipping, please check if the rear wheel is attached correctly. You can see how to properly attach the rear wheel here.
If you feel a full circle spin interval when shifting gears, try selecting one of the preset E-shifter settings in the app. If this doesn’t fix the issue, please contact customer support.