[Plugin: W3 Total Cache] Cannot Use Paging cache on Amazon WS

Hello,

I’m currently experiencing a strange problem with w3tc.
I’m running a multisite install of wordpress 3.5 with w3tc 0.9.2.11.

I’m trying to use page caching on the Amazon WS( which is my hoster ) and I can’t make it work ( Timestamp is refreshed on every request in the comments at the bottom of the source code of my page ). The strangest thing is that I also run the same website with the same setup on 2 other servers and everything is working properly on each server (which are totally different).

On my AWS install, it seems that Elasticache is correctly configured since I pass all set up tests.
It’s very strange and I can’t find a way to make it work.
Have you ever had this kind of problem on Amazon WS servers, or do you see any obvious reason why the plugin is not working ?

Thanks for your help !