membership and multilingual website - urgent

Well it's not the first time i am bringing up this problem but i really need urgently a solution for that.
We have a multilingual Magazine website with blocked content for members only, if you load the website as an normal visitor everything works fine in all languages but as soon somebody is doing a subscription over the membership plugin and logging in the navigation disappears completely ( there was one exception after updating to the menu didn't break but it broke again with and parts of the content in our main language it's not showing up and the other 2 languages the content disappears completely but as soon i change the member from subscriber to admin everything works okay. So i think the problem is not WPML but the Membership plugin.
I already tested the website with all plugins turned off (except Membership and WPML) and with the twenthyfourteen theme but still no navigation showing up and content gets broken.
Hope somebody can help me with this BIG problem besause we starting in the next days with a marketing and growdfundig campaign to gather subscribers.

Many thanks