Hyper-V 2012 R2 Failover Cluster - Moving Disk Failed

Hi,

I'm in the process of upgrading my hyper-v cluster hardware. We've been running a two node cluster for 5 years and the HP DL380 G7 are nearing EOL, so we bought 2 new HP DL 380 G9, connected them to the PS2000, added them to the cluster and everything is working. I can live migrated between all 4 nodes, back and forth no problem. The next is to evict the old DL 380 G7 nodes from the cluster, but before I do that I wanted to move all disks to one of the new nodes. This is where I get this error:

What's even stranger is that the new node are hosting some of the disks already (I assume they were automatically moved there, I didn't move any disk prior to this).

Any ideas or suggestions would be appreciated.

Thanks