Exit course button not displaying on black background

Hi there, 

I've noticed a change in how Articulate Rise publishes courses over the last little while. 

Previously, when I published a Rise course, the "Exit course" link/button in the top right would display on dark backgrounds with a white shade behind it to ensure it was always visible. This no longer seems to occur. See the attached screenshots. 

Does anyone have any ideas on how to resolve this issue?