ISCSI Initiator reports "Disk -1" ?

Hello,

i have a netgear NAS that acts as ISCSI Target for my Windows Server. The NAS has 2 NICs, which are configured with independent IP-Adresses: 192.168.100.2 and 192.168.101.2

My Server provides a counterpart for each NIC available: 192.168.100.1 and 192.168.101.1

The NAS should hosts 4 drives, which are setup as 4 LUNs and wrapped into 2 target-groups. The idea was to increase performance by connecting to both groups with an independent NIC. This worked perfectly fine when testing it with one disk per target-group. 

I tested this with one drive per group and testing was fine: about 198 MB/s throughput on a Simple-Disk with 2 Columns.

Now, I added one more disk and I am facing the problem, that the ISCSI-Initiator reports "Disk -1" for the two old disks.

iSCSI Initiator Report
=======================


List of Discovered Targets, Sessions and devices
==================================================

Target #0
========

	Target name = iqn.1994-11.com.netgear:nas1:57dea133:group100

	Session Details
	===============

		Session #1
	===========
		Number of Connections = 1

		Connection #1
		==============
			Target Address = 192.168.100.2
			 Target Port = 3260
		#0.  Disk -1
		========
			Address:Port 5: Bus 0: Target 0: LUN 0
		#1.  Disk 18
		========
			Address:Port 5: Bus 0: Target 0: LUN 1
Target #1
========

	Target name = iqn.1994-11.com.netgear:nas1:72ca59e5:group101

	Session Details
	===============

		Session #1
	===========
		Number of Connections = 1

		Connection #1
		==============
			Target Address = 192.168.101.2
			 Target Port = 3260
		#0.  Disk -1
		========
			Address:Port 5: Bus 0: Target 1: LUN 0

Also the Disk-Management shows "2 Disks Missing": 



However, Storage Pools are NOT reporting any problems with the ISCSI Disks (19&17, 18 not yet pooled):

so, is it "healty" now or not? May it be possible that Storage Spaces isn't able to catch missing ISCSI Disks and sends all the data to the disks without recognizing that no data is actually written???

Or is this just the "result" of pooled disks no longer appearing in Disk-Management? (So, The Initiator cannot find it, thus reporting "Disk -1" which in turn will make the Disk-Management think there is a missing disk?)

best,