I reset my profile and had it reload the UI. While walking through the steps to set it up, I got the following error when unchecking either "Enable turning in quests" or "Enable accepting quests" (not sure which one):

Message: Interface\FrameXML\OptionsPanelTemplates.lua:151: attempt to call method 'SetValue' (a nil value)
Time: Mon Jul 9 10:12:07 2018
Count: 2
Stack: Interface\FrameXML\OptionsPanelTemplates.lua:151: attempt to call method 'SetValue' (a nil value)
Interface\FrameXML\OptionsPanelTemplates.lua:151: in function BlizzardOptionsPanel_CheckButton_SetNewValue' Interface\FrameXML\OptionsPanelTemplates.lua:131: in function BlizzardOptionsPanel_CheckButton_OnClick'
[string ":OnClick"]:6: in function <[string ":OnClick"]:1>

Locals: checkButton = SUI_ATI_AcceptGeneralQuests {
0 =
newValue = "0"
}
isChecked = false
setting = "0"
(*temporary) = nil
(*temporary) = SUI_ATI_AcceptGeneralQuests {
0 =
newValue = "0"
}
(*temporary) = "0"
(*temporary) = "attempt to call method 'SetValue' (a nil value)"