ERG MODE Difference

Hello, for christmas i've bought a Tacx Flux 2, yesterday i have the chance to setup and test the trainer and everything was fine, but today i've made a trainingpeaks workout in zwift using erg mode and also record the activity on the garmin edge 530, on the bike i have double side stages powermeter.

ERG mode was setup at 170W on zwift and stages shows 20Watts LESS (Edit),  that's more than the claimed 2.5% of accuracy.

Here you can see the comparison files.

First five minutes was just on zwift.

Any advice on this?