SkyTimeOfDay / SkyDomeMesh look blocky on mobile

We’re trying to use the new SunSky-Actor and the material M_SkyTimeOfDay (Engine Content) for the SkyDome.
We’re deploying to Windows and Android (ES31) at the moment. In the Android the materials looks very strange.
Is there a possibility to fix this?

How it should look:

check the “full precision” in material