My Cloud EX2 failing to map correctly a My Book Duo


I recently purchased a My Cloud EX2 Ultra which I got configured as RAID0, so it is displayed as 1 unit.

Additionally I have a My Book Duo which is set as JBOD (each unit is displayed separately, Drive 1 and Drive 2).

When I connect the My Book Duo to the USB ports of the My Cloud EX2 Ultra to make it available on the network, it only maps/reads the Drive 2 (My_Book_Duo_25F6-2). It fails to show both drives. So I don´t have access to both. I got the feeling it identify them as the same which causes the problem but unsure how to fix this.

Could you please assist on how to make My Cloud EX2 to show both drives of the My Book Duo?

Many thanks