Titanium Backup insufficient storage while using external card android 5

I use Titanium Backup and on the newer Android when using external card for storing backups I was hit by this issue, manifested by backup session being interrupted with a message “Insufficient storage”.

I’m currently on Android 5.1.1 (CyanogenMod 12.1 NIGHTLY) and the following steps helped:

• Edit /system/etc/permissions/platform.xml

• Find the following section

<permission name="android.permission.WRITE_EXTERNAL_STORAGE" >
    <group gid="sdcard_r" />
    <group gid="sdcard_rw" />
</permission>

• Add <group gid=”media_rw” /> to make it look like that

<permission name="android.permission.WRITE_EXTERNAL_STORAGE" >
    <group gid="sdcard_r" />
    <group gid="sdcard_rw" />
     <group gid="media_rw" />
</permission>

• Reboot your phone