Weird problem with file permissions on ubuntu ?! Using ConfigurationLoader

Hey all,

I recently discovered a problem where some of our guest workers weren’t able to edit configurations of the plugins they maintain.
It turns out that the simple problem is, that the file permissions got changed to 600 when the configs were rewritten during the server start.
However I can not verify that this is a problem with our permission configuration as this seems only to happen with configurations that were written by a ConfigurationLoader retrieved using @DefaultConfig(sharedRoot = false)

I tested manually writing a file using a normal FileWriter which got the permissions it was supposed to get…

Maybe someone here has a clue what could cause this.
Oh, and by the way:
umask -> 0000

Permissions of parent dir:

/# file: fng.spongeutils/
# owner: Minecraft_MCMA
# group: fng_mc
# flags: -s-
user::rwx
user:Minecraft_MCMA:rwx
group::r-x
group:fng:rwx
group:fng_mc:r-x
mask::rwx
other::---
default:user::rwx
default:user:Minecraft_MCMA:rwx
default:group::r-x
default:group:fng:rwx
default:group:fng_mc:r-x
default:mask::rwx
default:other::---

Permission of file after rewrite:

 fng.spongeutils.conf
# file: fng.spongeutils.conf
# owner: Minecraft_MCMA
# group: fng_mc
user::rw-
user:Minecraft_MCMA:rwx         #effective:---
group::r-x                      #effective:---
group:fng:rwx                   #effective:---
group:fng_mc:r-x                #effective:---
mask::---
other::---

Permissions how they are supposed to be:

# file: testFile.json
# owner: Minecraft_MCMA
# group: fng_mc
user::rw-
user:Minecraft_MCMA:rwx         #effective:rw-
group::r-x                      #effective:r--
group:fng:rwx                   #effective:rw-
group:fng_mc:r-x                #effective:r--
mask::rw-
other::---