Resistance does not match downhill, flat road or uphill

Hi there I am experiencing issues with Zwift on my iMac or maybe my hometrainer a tacx flux. When I drive uphill I do not encounter resistance, almost the opposite, and watts fall. It happens also on flat stretches that I get the feeling of running uphill and watts rising. When I then drive downhill, it varies whether the resistance feels like downhill or uphill. I am connected to my iMac via the Bluetooth connection in the PC, and the trainer is close to the computer. Any idea of ​​what might be wrong?

I get the same issue. Can’t get hold of the zwift team to fix it