Hello,

I was able to replicate the undesired behavior you are experiencing with navigating to a subfolder by using the navigate method. I've created a sample project containing a Folder and a subfolder structure. Then on button click I use the navigate method to open the subfolder and observed the "Uncaught TypeError: Cannot read property 'loaded' of undefined" error occur.

I've logged this as a bug in our public Github repo for further research

https://github.com/telerik/kendo-ui-core/issues/6207

You could observe its status also from our public feedback portal where other users could also vote for raising its priority:
https://feedback.telerik.com/kendo-jquery-ui/1500317-filemanager-navigate-method-throws-an-error-when-navigating-to-a-subfolder


The error is not thrown if separating the navigation and calling the navigation to a subfolder in a timeout:

var fileManager = $("#filemanager").data("kendoFileManager");
            fileManager.navigate("Images");
            setTimeout(function () { fileManager.navigate("Images/NestedFolder"); }, 200);

Best Regards,
Misho
Progress Telerik