Hyper V filling drive, struggling to shrink

I have a client with server 2012 running hyper-v hosting 2 x VHDX. One of the VHDX is dynamically expanding and filling the drive making them both pause.

I am unable to mount the drives in disk management, when I do the drives appear for a second and then vanish, however they mount in read only mode fine. There is a partition of free space (1Tb) on one of the drives which I need to zero out and remove or use a partition tool to move this to after the active volume.

Anyone have any ideas why the drives wont mount with write access in Disk management (or any other ways to zero the data and shrink the VM)
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David Johnson, CD, MVPOwnerCommented:
If a drive is filling up and in so filling up the physical drive you have oversubscribed the virtual drives.  The solution is simple 'add more storage'. you can then move the virtual drives to the new space.
eruditAuthor Commented:
I fixed this by restoring the previous nights backup onto the logical drive, deleting white space with sdelete, defragging the disk and using disk2vhd to reconvert to a VM.

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eruditAuthor Commented:
No other comments helped - worked it out for myself
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