Sync duplicate shared folder

Hi folks

I have a very big issue with my owncloud 9.1.2 running behind a NGINX reverse proxy and the owncloud mobile app on Android Phone

Let me explain :

Expected behaviour
User1 share FOLDER with user2
User2 log on mobile app and see FOLDER.
User2 quit mobile app and come back later, FOLDER still here.

Actual behaviour
User1 share FOLDER with user2
User2 log on mobile app and see FOLDER the first time.
User2 quit mobile app and come back later, FOLDER has been renamed in FOLDER (2)
User2 quit mobile app and come back later, FOLDER (2) has been renamed in FOLDER (2) (2)
User2 quit mobile app and come back later, FOLDER (2) (2) has been renamed in FOLDER (2) (2) (2)
...and so on.

Environment data

ownCloud 9.1.2 installed Debian 8 running PHP7 behind a NGINX reverse proxy using SSL

Android version: 5.0.2

Device model: LeTV X600

Stock or customized system: stock

ownCloud app version: 2.2.4 on PC

ownCloud server version: 9.1.2

Logs

don't have any atm but i can investigate to get them if necessary.

Note : I really think that the issue is due to NGINX reverse proxy configuration because i have another owncloud installation running on the same Debian 8 with SSL and it work like a charm on mobile app...

Thx for any help...

It might be also caused because you're using an outdated ownCloud version.