Custom Export Web Map instances in ArcGIS for Server 10.2.2 are not generating new tokens after the token has expired, resulting in failures until a new instance is used.
1. Use ArcGIS for Server 10.2 or 10.2.1.2. Instead of customizing the Export Web Map tool, have the application pass tokens in the webmap JSON.3. Use Python to pre-process the webmap JSON and add a token prior to sending it through the Export Web Map task (see sample: <a href="http://github.com/djarrard/WebmapWrappers/tree/master/InsertToken" target="_blank">github.com/djarrard/WebmapWrappers/tree/master/InsertToken</a>).