@Carlos_Junod - it looks like the affected text is bold in your post screenshot, and for some reason isn’t bold in the build; if you’re still trying to resolve this, are you able to post a screenshot of one of the affected text elements and its settings in the Unity inspector window?
@Vaughan_MacEgan - the overlay order is (as far as I can tell) based on the hierarchy order (at least in 2D). If you want an image under your text, make sure the image is below the text elements in your hierarchy, for example:
Here (with a bit of luck!) you can see that the ‘you win’ splash covers over the ‘range’ (orange) text, and the ‘start button’ (red) text covers over both of them - this matches the hierarchy order (Range, Image, Start Button), and if you shuffle them around, the way they layer over each other changes accordingly.