Serie 3500 not refreshing Synology Media Server contents

My 3500 TV is connected on a Synology 413j NAS, running Media Server.

I basically have two major problems here :

Files which worked yesterday won't be seen anymore today (although I made no modifications ...)
When I add files in the Media folders on Synology, they don't show in the TV browse screen of the Media Server.

Looks like it doesn't refresh an internal cache. Same if I modify the name of a folder - it still shows on TV with the old name.

Any help appreciated.

I confirm this behavior after some more tests :

- I stopped the sharing in all other devices on the network (to avoid possible circumvention of the Media server)

- I reinstalled the factory settings, and did the TV software update again

- I suppressed many movies on the Media Server, in order to have a clear view of the new configuration

- I monitor the connections on the Media server

NOW, here are the results :

- The TV shows correctly the tree : FOLDER > Music - Video - Photo

- The TV shows an OLD snapshot of the contents, including the discarded files (! -> some cache is very persistent here)

- The TV DOES NOT appear as connected on the DLNA Media Server (!!)

- When I try to play one of the 'ghost' files, it simply EITHER gives a black screen, OR says that the file is not supported (quite logical, since the file is no longer present !)

I suspected a malfunction of the DLNA Media Server.
So I accessed the same MEdia Server using the DLNA capacity of my LG BlueRay player. All files appeared correctly and refreshed correctly.

So the question remains : How can I get rid of this caching system of the TV ?