[Q] TWRP SD card issues topic

Hi Xda members,

I'am running TWRP 2.8.3.0 everything seems to work fine except with my Micro sd.
I got acces problem to my external SD card, it look permission problems,

When i try to reformat the sd card i get this error:

E: Unable to Unmount '/external_sd'
E: Error changing file system

When i try to make a backup this one:

E: Unable to create folder: /external_sd/TWRP (errno=30)
E: Failed to make Backup folder.

In install i'am able to access to external_sd and view the files inside.

Here is my config:
S4 GT-I9505
Android 4.4.2
ROM: stock rom I9505ZHUFNL1
Rooted with CF autoroot
Recovery: TWRP 2.8.3.0

I tried the fix permission button in TWRP but it didnt worked.
I also tried to install Extsdcardfix-flashable.zip from this thread: forum.xda-developers.com/showthread.php?t=2607215
Did some factory reset, reinstalling everything and this didnt worked.
Reformating the External sd via stock rom work.

I've been looking around the web trying to find some solutions but nothing do so far and i run out of ideas.
So if anyone have some ways to fix it i'll really enjoy it.

Thanks for your time,
Ankhaz