I'm having the same duplicate world bug with Chestnut Ridge (not mod related). Unfortunately I'm also experiencing the corrupted traits/CAS bug in the same save file. Thankfully I've only opened this save file, so I'm hoping the bugs are contained. But I'm afraid that backing up that save file's household's to my library, in order to fix the duplicate worlds bug, will spread the CAS bug.
Any advice on alternative ways to fix the duplicate world issue?
I found a trigger for this duplicate world issue which I managed to repro multiple times - launching the game whilst downloading/installing a Pack in the background. For me it was in Origin but I should imagine the same could be applied to EA App too and possibly console.
To fix it I quit the game without saving, trashed the pack with the duplicate world (EP14 in my case), repaired the game then re-downloaded the pack. Repairing may not have been necessary but I did it as a precautionary measure.
I'm on a Mac, pack folders in macOS can be found in the Sims 4 Packs folder which is in the same location the base game is installed to.
July - last edited July
Merged your post into the bug report. Assuming you are on a Mac, because you posted in the Origin forum, trash the EP14 folder in your Sims 4 Packs folder and re-dwonload it (see my post above yours). Also see Crin's solution on page 1 for help with any effect this may have on saves and households.
Out of interest, did you load the game whils downloading the pack?
I'm on a PC. I have all the packs. I just got Horse Ranch yesterday. DLed & installed. Got a duplicate Horse Ranch world.
Dumped Zerbu's All Worlds are Residential mod, then dumped other mods, then dumped all mods, deleted Horse Ranch folder & reinstalled, repaired game in between these several times, no effect. Duplicate was still there.
Completely uninstalled the game and reinstalled with all expansions. This got rid of the duplicate world. Added mods back in one folder at a time. This went well until I added my build/buy CC back in. Duplicate world reappeared.
I took the build/buy folder back out to do a 50/50 and the duplicate world was still there. Took all mods out and the duplicate was still there.
I can't do a 50/50 if the game won't reset when I take the mods out. So I guess I'm stuck with 2 worlds now unless/until there's a fix.
Thanks for reading.