To add another datapoint:
My rig: Cycleops JetFluidPRO trainer + Assioma Power Meter Pedals (DUO) + Zwift for Apple TV 4K. Bluetooth communication between pedals (with built-in Cadence), Wahoo HRM, and Apple TV.
For months, this set up has been working perfectly for me. The power displayed on screen in Zwift has always been within 3 - 5 watts of power reported on my Wahoo ELEMNT Bolt head unit. Then, sometime between July 25 and Aug 2, something changed which resulted in what Stuart reported above . That is, Zwift now reports one-half the actual power output. I know there has not been a firmware update to the pedals in that time. So I suspect something in a recent Zwift update broke what was otherwise working perfectly for me. So for now, have to rely on Virtual power (based on power curve of trainer + speed sensor) for Zwift rides.
I hope this helps isolate and solve the problem for good!