It takes near 2 minutes to launch published desktop when desktop lock is enabled.
 

Caution! Using Registry Editor incorrectly can cause serious problems that might require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.

1. Add Citrix recommended antivirus exclusions following sections both Receiver for Windows and XenDesktop 7.x Client OS VDA in https://www.citrix.com/blogs/2016/12/02/citrix-recommended-antivirus-exclusions/

2. Add below registry item and set relevant values on the client  
32-bit Windows
HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\Dazzle
Name: LiveInDesktopDisconnectonLock
Type: REG_SZ
Value: False
64-bit Windows
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\Dazzle
Name: LiveInDesktopDisconnectonLock
Type: REG_SZ
Value: False

3. Add below registry item and set relevant values in VDA 
Registry item 2:
32-bit
HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\Logon
Name: DisableStatus
Type: REG_DWORD
Value: 00000001
64-bit
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\Logon
Name: DisableStatus
Type: REG_DWORD
Value: 00000001
 

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Problem Cause

https://www.citrix.com/blogs/2016/12/02/citrix-recommended-antivirus-exclusions/