In patch 18.104.22.16888: Added support for common GlueXML and FrameXML code has moved some files and dependencies to 'SharedXML' folder in the game data, and changed the load paths for several elements. This change went live with patch 22.214.171.12445, which is in the current set of 'live' client patches as of patch 126.96.36.19988.
In patch 5.4.8, calling SetUIVisibility(false) is now "protected". Setting 'true' is still not protected. 
In 188.8.131.5298 patch (currently through game version 18019) is a XML element case error in common file SharedUIPanelTemplates.xml for UIPanelGoldButtonTemplate, where 'OnMouseDown' and 'OnMouseUp' are actually spelled 'OnMousedown' and 'OnMouseup'.