QGIS 2.14.6 Processing Extension, 'Polygonize' Tool missing

1. 
   

   Just installed QGIS 2.14.6 64Bit from OSGEO4W installer. Processing extension Version is 2.12.99. As can be seen in the screenshot, I'm not able to switch to 'Advanced Interface' as usual in order to access the Polygonize Tool (Lines to Polygons does still not work, cp. QGIS 2.12 Lines to Polygons not work properly):

   
   

   

   
   


2. 
   

   Same installation run parallel on another machine has Processing Plugin Version 2.10.3, and here I'm able to switch to advanced Interface and access the Polygonize tool:

   
   

   

   
   

Add/Update:

3. 
   

   Completely confusing: In 2.14.5 installed from the standalone installer the processing plugin version is 2.12.99 too, but herein I can access the Polyonize tool:

   
   

   

   
   

Research effort so far: I realised that in case 2. the processing plugin was installed under username\.qgis2\python\plugins\, unusual path for a core plugin. Obviously (or maybe?) the problem is a previous installation of QGIS before processing has become a core plugin, so the plugins herein seem to override core plugins. This would explain too, why the plugin under 2. is not affected by the update (since processing is a core plugin, it is not available in the repository). The solution was simply to uninstall the plugin, restart QGIS and the core plugin version 2.12.99 is available. Remarkable: Polygonize Tool is still available (in contrast to case 1.). So far so good.

To sum it all up:

In all three cases processing plugin version is 2.12.99:

1. OSGeo4W installer, No Polygonize Tool


2. OSGeo4W installer, Polygonize Tool available


3. Standalone installer, Polygonize Tool available

So what can be the problem in case 1? May I have missed something in the OSGeo4W installer?

Answer

As the Processing plugin has become core, you don't need the .qgis2/ version anymore.

In the recent QGIS version, the plugin can be found in (for example, in QGIS 2.16.1 standalone):

C:/Program Files/QGIS 2.16.1/apps/qgis/python/plugins/processing

So not only it is safe to delete the .qgis2/ version, it may be advised as it could help avoid conflict with the core version.