Text Entry Variable: When Control Loses Focus places yellow rectangle on my slide

Hello! I am working on a simulation module where users enter information into screens that mimic the system they will use in real life. One step they need to do is to enter text into a field. I have the Text Variables setup and working well (showing correct feedback / incorrect feedback layers as appropriate) but I am also getting a 'random' yellow rectangle in the bottom right of my screen when the user clicks outside the text box, or press any key on their keyboard. Does anyone know what is causing the yellow box to appear, or how I remove it?