We just purchased a Reebok (Sole) Z-Tech treadmill, designed to work with Zwift via tablet. I was unable to get our up-to-date iPad (17.7.10) to run Zwift properly. As the treadmill is new, I suspected there was likely an issue with that device/bluetooth dongle (firmware also updated), but testing running Zwift on the iPad with my Wahoo bike trainer yielded similar results. I have no issues on the bike via AppleTV with iPad running the companion app.
On the treadmill I immediately have a connection failure notice in the upper left, though I can manage 15-30 seconds of my avatar moving before Zwift crashes completely. On the bike Zwift crashed before I turned a single pedal rotation.