First, my setup:
Computrainer in Erg mode (cadence not hooked up, don’t think that matters).
Bike with Quarq and a garmin 520 in indoor mode (the pwoermeter and swift track nicely). I have the garmin file in addition to the file in Zwift for comparison if your developers need them.
I did the 2nd day of the 12 week FTP workout just now and failed both of the 5X10sec @ 440 watt sections. It made me sad. Worse is that I don’t think I actually should have failed. The resistance on the computrainer would not raise fast enough but a combination of high cadence and it eventually kicking up the resistance got me over for a significant portion of the interval on the garmin/quarq combo. Zwift would often not update the current wattage (I don’t know the averaging it’s doing but perhaps it could be lowered or power could be sampled more on shorter efforts).
I tried to hit the intervals differently a few times. Like starting my effort before the red gate or waiting until 1 second in but couldn’t find rhyme or reason to why swift would update the power sometimes but not others. I’ve read about ramp rate issues with the kickr on the wattage list ad nauseam but I’ve never experienced in on my Computrainer before.
Let me know if you’d like the garmin file. Other than this I’m really liking the workout mode.