The Ext.io.ux.Strings.* variables used statically in Ext/io/ux/ChangePassword.js and Ext/io/ux/AuthSencha.js result in a race-condition-induced intermittent loader failure, because listing Ext.io.ux.Strings in Ext.io.Controller's requirements doesn't ensure that its source code is evaluated before other class definitions'.
I've wrestled with this problem on my own and would be interested to see Sencha's solution, but static class members can't be depended on when class definitions are evaluated.