On a specific workstation, a warning is displayed in AWI stating "Not a valid AE import file" when trying to Import a XML file.
Nevertheless, if the Error Popup is closed and the page refreshed, it can be observed that the Object was created.
On other Tomcat / AE Systems / Internet Browsers, the issue does not occur.
No error messages appear on AE / AWI logs.
Web Browser cache
Release : 12.x
Component : AUTOMATION ENGINE
Issue due to the Web Browser cache, using another browser from the same workstation proved that the issue was not present.
After clearing the Web Browser cache, the issue was no longer occurring.
See instructions for the different browsers here