Same problem here - or at least a very similar one.
I display a digital clock below some analogue watch hands, but I use a tag expression on the Y-coordinate to move it to the top if that area is occluded by the watch hands. This expression works fine in the WFS preview, but it is ignored on the real GW4 and on the Wear OS 3 emulator in Android Studio, and the clock never ends up moving. Some very simple expressions do seem to work, but anything non-trivial breaks down and gets ignored.
Here’s a simple test case design which demonstrates the problem.
Set the time to e.g. 18:30 and the clock will move to the top of the watch face in the WFS preview, but not on the actual watch.
It’s a shame as this worked really well on GWD/Tizen!
Edit: actually I’m not using SC_PER myself, but only time elements - so perhaps a different issue after all? The expression is
-196*(((([MIN]>=25)*([MIN]<35)*([HOUR_1_12]<11))+((([HOUR_1_12]==5)+([HOUR_1_12]==6))*([MIN]>=5)*([MIN]<55)))>=1) in my case.