Wheel on or direct-drive (wheel off)?
On my 2017 Kickr direct-drive, the only time I’ve had weird resistance changes was due to shifting lighting (sun bouncing off light concrete flooring in the garage, and shadows from overhead lights). Except for the original gen1 Kickr, Wahoo uses an optical sensor to estimate power. Putting a black mat on the concrete floor resolved the problem. That was suggested by Wahoo support, and it worked.