I had this issue after upgrading from 4.14.1 to 4.16.1. It only showed up in the log when I built a server in the Frontend tool. It did not appear when I built the game in the editor. The error message was a bit confusing, maybe you could improve that. It had me thinking that I needed to re-save the asset that used the enum but that didn’t work. I opened the enum in the editor and saved it. The warning went away.