First of all, make sure this plugin: System - Cache is unpublished.
Then; try disabling/unpublishing the "One page Checkout" plugin you use and try again?
FYI: This problem might be caused because of a "cache" as well. Try to disable the Joomla Cache from Joomla Global Configurations. . -ALSO- if you are using any 3rd party cache plugin, disable them as well. -- Open the Joomla Plugin Manager and search for "cache" keyword to find the cache related plugin(s)
You can install a fresh Joomla, use beez_20 template (which is the template that comes with Joomla by default) then install that cache plugin.. You will get the exact same problem.
So, what i am saying is; you can't blame our template for this problem. You should blame jWECache. That plugin shouldn't cache the whole pages, instead it should cache the db objects or cache the part of the pages only (modules). If the cache plugin doesn't work the way it was supposed to work.. then i can't help you with that.
3rd party CACHE plugins are always problematic (especially the free ones) and you shouldn't use them unless you have a static joomla site. You should only activate the Joomla's Official CACHE from the Joomla Global Configuration. No more.
Did you try to contact with the developer of jWECache and see what they say?
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