Am having this very issue. I’m in 4.23.1. Sadly we are not alone, but at least, we are not alone. 
In my case, when this error started popping up, an issue arose where my key bindings don’t work when a level is opened from my Start Menu. If I open levels without using the start menu, bindings work fine. Opened from my Start Menu, and pressing keys, mouse… nothing. I have escape binded to “quit level”, and curiously that does work in PIE. If launching in standalone, escape does not work along with the rest of the bindings. Hmm.
Having to send around packaged progress demos without the StartMenu enabled, with “game over” state returning the player directly into the first level again. Bummer. Anyone with a solution to this particular outcrop of this duplicate world setting issue? Assuming that is where it’s coming from? I’m guessing this is the case since the key binding issue cropped up the same time the dupey world error arrived.