FAQ: Why are there multiple DISPLAY SCREENS overlaid with one another in my experiment?
There are a variety of transparency settings in Experiment Builder to allow screen resources to interact differently with the background and other screen resources. However, when used incorrectly these settings can cause strange behavior such as seeing objects overlay one another rather than getting rewritten or seeing through parts of objects which should otherwise be solid.

To avoid seeing multiple display screens at once, and other problematic transparency issues (such as white dots or missing pixels), please make sure that the Transparency color (Edit menu -> Preferences -> Devices -> Display -> Click on the box left of "Transparency Color" to open prompt) is set to a color that is close to, but not exactly the same as, the background color of the DISPLAY_SCREEN actions. For example, if you are using a white background in the DISPLAY_SCREEN nodes (RGB - 255, 255, 255) then the Transparency Color property of the project should be set to near white (e.g. 254, 254, 254).