This script adds a service dependency on the CCMEXEC service to ensure SMSTSMGR has started first. See the blog article http://www.potentengineer.com/task-sequence-stuck-installing-in-software-center/ for more information.

Update 3rd July - The script has been updated after some testing found that the service dependencies had been in reverse. The DCM cab will be updated in the next few days.

The DCM version is available here - https://gallery.technet.microsoft.com/Add-SMSTSMGR-Service-7524d468

PowerShell
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# Fix for Software center show application stuck at Installing  
# https://social.technet.microsoft.com/Forums/en-US/e382da34-079c-4619-8fdb-e5e44c436857/software-center-show-application-stuck-at-installing?forum=configmanagerapps  
# Add service dependency for SMSTSMGR against CCMEXEC  
# Author: Mike Palmer  
# Date: 3rd July 2015  
# Version: 1.01 
  
# Get Service Details  
$service = get-service smstsmgr 
  
# Check ServiceDependedOn Array  
if (($service.ServicesDependedOn).name -notcontains "ccmexec")  
{  
 write-host "Not present...Configuring Service"  
 start-process sc.exe -ArgumentList "config smstsmgr depend= winmgmt/ccmexec" -wait  
}  
else  
{  
 write-host "Present..Taking no action"  
}