Updating 3^rd party software in a vDisk or vDisk version including but not limited to, Windows Updates, hypervisor specific network tools & drivers, security software, medical imaging software and more results in a Target Device BSOD, hang or freeze, post install.  The vDisk may be required to be “reverse imaged” in order to proceed.

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Reverse Image is the process of taking a working vdisk and imaging (cloning) a new disk that is locally attached to the target for the purpose of resetting the Target drivers within an image. The first step after performing the reverse image where the vm can now boot from its local drive without BDM/PXE is to uninstall the PVS software.  Since the PVS software install is the last step prior to creating a new vDisk or updating an existing vDisk you can now perform all 3^rd party updates after the uninstall and subsequent reboot. 

Reverse Image General Process:

1. Create a new vDisk version and put it in maintenance mode or Private image mode (read/write).
2. On your maintenance vm (preferably the Master Target Device) via the hypervisor remove the cache drive and add a hard drive large enough to accommodate the vDisk being imaged.
3. PXE/BDM boot your Master Target Device to the read/write image.         
   1. You may have to mark the new disk online in disk manager.
4. Launch P2PVS:

5. Boot to your newly imaged locally attached disk and uninstall the PVS target software.
6. You can now add or update any third party drivers like VM tools or antivirus client software etc.
7. The last step prior to running the imaging wizard and creating a nw vDisk or re-creating an existing vDisk is to install the PVS Software.  Please note that installing the PVS Target Software requires that the Device did not first BDM/PXE boot.  The boot order must be set to DISK first in BIOS/EFI or the PVS Target software will fail to install.  Once installed you can follow the prompts to run the Imaging Wizard.  After the first part of the imaging wizard is complete and a reboot is required to finish, you will be required to set the BIOS/EFI back to either NIC or CD depending on the use of BDM or PXE before the machine reboots again.  This second portion of Imaging requires a PXE boot to local disk which the wizard configures for you in the console after the first portion of the wizard is complete.

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Problem Cause

The Target Device drivers are designed to allow for disk IO redirection over the LAN.  The two main Device drivers, Bnistack6 and CvhdMp, the network protocol driver and storage filter work in tandem to detect and transmit Read and Write IO.  When the relationship between these drivers has been changed or the stack has been altered by 3rd party drivers or one of the drivers by itself is being impeded by another source results in the typical BSOD or target hang.  Disk is an essential component of the VM therefore many PVS issues can result in the same observed Target behavior, when disk IO doesn't flow the endpoint becomes inoperable.

Reverse image can be performed using HyperV.  Copy the existing .VHDX (must have created new merged base if versions exist) from the PVS store to HyperV> In HyperV create a new vm and use the existing hard drive (.vhdx file)> Boot the new VM, uninstall PVS, perform 3^rd party updates, reinstall PVS> copy from HyperV back to the PVS store.
Reverse Image will soon be handled within Citrix IPS removing the need to follow the original legacy process.  It may exist more as a backup or standby method if necessary.  

https://docs.citrix.com/en-us/tech-zone/learn/tech-briefs/image-portability-service.html