Menu-editor tree issues

Dragging and dropping menu items in the menu-editor tree seems to work erratically. Some problems observed

• Occasional error 'A technical error occurred' without any logged info
• Unpredictable when item is indented when dragging to the left or right (nesting menu's)
• After adding multiple menu items, multiple dropzones appear.
• Sometimes menu items are duplicated in the tree (see screenshot). Both menu entries shown (actually one menu item) are highlighted when one is clicked
• Occasional stacktrace:

[INFO] [talledLocalContainer] 04.03.2015 11:49:16 WARN [org.apache.cxf.jaxrs.impl.WebApplicationExceptionMapper.toResponse():72] javax.ws.rs.InternalServerErrorException: HTTP 500 Internal Server Error
[INFO] [talledLocalContainer] Caused by: com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "isNew" (class org.hippoecm.hst.pagecomposer.jaxrs.model.SiteMenuItemRepresentation), not marked as ignorable (10 known properties: "items", "repositoryBased", "pathInfo", "linkType", "localParameters", "title", "link", "id", "roles", "mountPath"])
[INFO] [talledLocalContainer] at [Source: org.apache.cxf.transport.http.AbstractHTTPDestination$1@113f2f7d; line: 1, column: 223] (through reference chain: org.hippoecm.hst.pagecomposer.jaxrs.model.SiteMenuItemRepresentation["isNew"])