I have a Tacx Neo 2 and 4iiii left sided power meters. If I run them both indoors the 4iiii reads 5-10% higher on average. I expect a fair proportion of the difference is drive chain loss, and some may be leg length imbalance.
I’ve noticed when comparing the two that the Tacx goes down to zero roughly once every five minutes. Could this be down to drop out between the Tacx and Zwift? And might it be part of the reason for the difference?