AeroPod, PowerPod and Newton

I used PowerPod v3 for about a year on my mountain bike (old Scott Scale 710) . Because of the quarantine, I'm forced to use it on my Minoura MoZ Roller connected to Zwift with Garmin 830 bundled with Speed, Cadence, and HR. I notice a difference in Speed on Garmin and Swift on a flat road. My Garmi...