Hello,
I have a problem when I try to create a package for Win64.
I see in the log file this error :
UATHelper: Packaging (Windows (64-bit)): Program.Main: ERROR: AutomationTool terminated with exception: System.ArgumentException: Un élément avec la même clé a déjà été ajouté.
I’m lost 
I attach the little but complete log file…
Thanks for your help !
I found the problem, I just delete the Saved folder in the project and all work perfectly !
Thank you this saved me a lot of time trying to solve the issue!
did not work for me An item with the same key has already been added.
anyone have another fix?
Just delete the Plugins folder from you project file and put plugging in the engine folder and enable it by searching this will fix I am working on it for a long time
Check if you have a plugin installed in the project folder and the same plugin installed also in the Engine.
none of the options worked for me. I deleted saved folder, also checked for a duplicate plugin in the project folder but still receiving the same error. any other solution?
did you ever figure out what the issue was? I’m having the same issue and adding to yours, searching for a file called .target within the project yielded no results