I have found that if the Kickr loses its ANT+ connection with Zwift then the Kickr can misbehave, where the resistance remains the same no matter what the gradient is on Zwift island.
I use my Kickr in the garage and decided to bring my PC back indoors while I took a short break. I left the PC running Zwift albeit paused when I brought it in. It would have lost ANT+ connection with the Kickr. When I took the PC back out to the garage, and resumed my ride I noticed that the resistance never changed. I tried to unpair the Kickr but no luck. I also tried removing the ANT+ dongle, but that is a very bad thing… If you do this mid ride then you will never be able to resume riding.
I realise it is harsh treatment to move the PC out of range of the Kickr, midway through a ride, but it is interesting that when the PC was back in range the ANT+ comes resumed again without any issues. I was only the Kickr that misbehaved.