@ZargonDaWiked sorry to hear about these issues. We’re tracking various issues of this type currently. I was able to reproduce your issue following the steps here: When importing buildings directly from fortnite in flying man mode the project does not pass validation and does not start giving error messages - #12 by HalcyonKnight96 but after hitting the errors I was able to work around them by deleting the device in the UEFN editor.
Did you happen to add this device to your project while in Creative mode with the phone tool?