If you define your own UI elements you SHOULD set the drawTier and drawLayer and drawLevel explicitly for all of your controls as they don't have a defined draw* and may fall behind other or above other UI elements because of that.
At least give them some low default values so they do not overlay other vanilla UI controls nor any addons.
Always puting them to the highest values e.g. will make them even show ABOVE context menus! So don't do that
WIKI:
https://wiki.esoui.com/Drawing_Order