Elite TUO Watt output way too high while climbing

Hi Guys!
I’m at a complete loss here. I own an Elite TUO wheel-on trainer for 2 weeks now. It took a while to calibrate it via the Elite myETraining app but finally it worked. I didn’t calibrate it via Zwift, since there’s a known issue with the speed readings.
Anyways, in order to compare accuracy I was using Zwift with the bike of my father, which has a powermeter installed. When using the TUO without the powermeter, watt output on the flat is off by about 20 - 30 watts - which would be OK. BUT everytime I’m ascending it’s off by 150 - 300 watts. For instance, when I climb a gradient of 10% it shows 550 watts and more, which is obviously wrong. 250 - 300 I got while riding with the powermeter. Now did anyone else experience something similar?
I recalibrated the TUO several times, I’m sure that I set my weight correctly and I even contacted Elites customer support. But nothing so far. Am I not allowed to shift while the calibration process? Is Zwift missreading something?
Any sort of help would be much appreciated, because it takes away the fun of zwifting having wrong watts going uphill.
Regards

Hello,

I have similar problems, but not to your extent.
I don‘t own a power meter, so I cannot provide any exact figures, but I have the feeling that it gets way easier to hold a certain wattage when going uphill, compared to flats.

On a flat course (Tick Tock), 245 watts for 40 minutes feel about the same as 305 watts on Alpe de Zwift for the same duration, my heart rate is also quite similar. Likewise it feels a lot harder to pedal the same power downhill. To me it feels like when going uphill the trainer thinks it added more resistance than it actually does but calculates the power as if it did. Vice versa when going downhill.

50 % difficulty or 100% difficulty made no difference on the perceived effect, but I am going to try with 0%.