Zwift support really haven’t been very helpful (most of their suggestions aren’t even relevant to the problems I was having, and with messages going backwards and forwards they suggest things you’ve previously told them you’ve already tried…). Anyway, when I decided to give Wahoo a try, just in case it was a fault with the Kickr 2016, they replied saying bluetooth support in Zwift was relatively new and was still unreliable. They recommended getting an ANT+ dongle. I did this and everything has worked perfectly so far (2 x 1hour+ rides). I also got myself a new Tickr and connect that by ANT+ (even though I wasn’t having issues with the old one), but my old Blue SC (which is the old bluetooth only version) still connects via Zwift Mobile Link app - and that’s been working fine.
Given that the new iOS version will be Bluetooth only, I hope they sort out these issues. It’s a shame Zwift don’t acknowledge them - Wahoo have clearly seen a lot of people having bluetooth issues when using Zwift.