If you have multiple Citrix Provisioning Servers in your farm yet are having some clients freeze/hang when one of the stream services shut down, you might have a simple configuration issue within the Citrix Provisioning Services Console.
After verifying that all vDisks are available and accessible from all Provisioning Servers, check out these additional configuration options.
Verify that the Store is set to service all Provisioning Servers.
Verify that the actual vDisk is set for High Availability.
Verify that the vDisk is set to use a load balancing algorithm and not assigned to a particular Provisioning Server.
Check the Bootstrap configuration for ALL Provisioning servers to make sure all Provisioning Servers are listed correctly. Incorrect setting in the Bootstrap configuration will affect fail over behavior.