EX4100 does not mount wd book duo


I was able to get a EX4100 with 32 TB very cheap. I know that OS 5 is kinda buggy and therefore I didn’t update to it. The latest OS 3 is installed.

Now I try to use my WD BOOK DUO (Raid 1 Setting, setup on my Windows 10) with the NAS. I partitioned it with NTFS and used GPT (3 TB HDDs). Sadly the NAS doesn’t mount it.

I found out that if I use NTFS and MBR (with one 2 TB partition) it mounts the device. If the WD BOOK DUO is connected during EX4100 startup the ui dashboard hangs with “the system is booting up, please wait…”. The SMB-Share works and SSH works too. If I disconnect the WD BOOK DUO and restart it again the ui dashboard works.

Any ideas? I only need a stable NAS in my LAN, I don’t need cloud features. And if I want them I would install a VPN. Should I update to OS5?