Watch Face is unable to switch to ambient mode

After reloading the watch face from the WatchMaker app directly of with Tasker "Change Watch" action the watch face is unable to switch to ambient mode on first try. Screen goes darker as expected, but the watch face stays the same, only the second hand stops.
After waking up the watch and waiting for another timeout watch face is mostly succeeding to switch to ambient mode (sometimes it needs a one more try).
This happens on Android Wear 2.0, it was fine on 1.5.