That sounds like a funky bug! I'm not sure why it's not saving. I remember there were problems like this when they first developed Default Page Settings, but it was thought that all this kind of bugs was fixed. Since I've never (chosen to) used a non-transparent Default Tint, i've not tested this yet. Used to have some problems with Default Page Size Settings not sticking, but that was fixed back then. This does SOUND similar from that time. Hopefully the Roll20 Team will help you test and diagnose and fix this.