Usually problems with the designer is to incorrect initialization javascript library.

For the designer is required:

• JQuery
• JQuery UI
• JQuery.treeTable
• KineticJS v 5

For the diagnosis troubles You need open console browser (usually opened by pressing F12 button).

Typically, the error associated with:

1. Error: "Object does not support property or method 'dialog'"

You don't initialize library JqueryUI or you have included JqueryUI twice.

2. Error: "Unhandled exception at line 5, column ....... in ...../Scripts/workflowdesigner.min.js"

You are using an incompatible version of jQuery.

Please use this scripts from: jquery.js and jquery-ui.

3. Problems with mouse control in Chrome

In some cases AdBloсk blocks some mouse events.

To resolve the need to disable AdBloсk and restart your browser.

4. Error: "Object doesn't support property or method 'addEventListener'" in InternetExplorer

Follow this instructions: http://social.technet.microsoft.com/wiki/contents/articles/24276.sharepoint-2013-troubleshooting-object-doesn-t-support-property-or-method-addeventlistener-or-getattribute.aspx

5. Error: "0x... - JavaScript runtime error: Unspecified error." from kinetic.js library

This happens when it can not download images. Check that the path to images that is configured for the Designer object at  imagefolder: '/images/' property exists and contains images fro the Designer.