The system of scandals involving royalty and legacy is having problems.

I'm having the same and I play in console so no mods, and also that purple cloud never goes away even if I deactivate the scandal system 

It happens to my sim too! I also drank a negative moodlet dissolver potion and it disappeared for only a few hours and then it reappeared 

Tried and solved! 
1.Make them be caught in another scandal. 
2. Release Scandal
3. Then go more choices, more choices until you you see " Toggle the floating scandal cloud effect off/on".

All this did was give me two scandals on top of each other.

I also have this issue. Deactivating scandals in game play does nothing. The only option on the Scandal on the computer is to buy a secret. The moodlet has expired but the cloud will not go.

You do not need to create another scandal to toggle on/off the dark cloud,it will be on over sims head if you are already in a scandal,Also what you can try to do is, disable scandal in option, wait for scadal to disappear and then re-enable it again.

That doesn't make sense, Blaine rocky. You don't need to create another scandal just... get into a scandal?  Huh?