RDP/Terminal services Client (MSTSC.EXE) published as a seamless app in Virtual Apps and desktops 1912 cu2 to Cu4 crashes, the issue can usually also be recreated launching MSTSC.EXE from a published desktop. 

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.

This is a known issue [CVADHELP-18694] which has been fixed in 1912 LTSR CU5 and 2203 LTSR.

The recommended course of action is to upgrade to one of these LTSR versions. 

However, if you cannot upgrade immediately, you can use the following workaround:

1. In the registry of the VDA, go to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Authentication\Credential Provider Filters\{3571A91D-713C-427c-AA0C-BBF4F618A819}
2. Set the DWORD Value "Disabled" to 1 - if this value does not exist, create it.

Warning: This registry change disables CitrixRemoteLogonFilter, so there is a small chance you may encounter other unexpected behaviours. Test the change before deploying to production to ensure all apps and desktops using the VDA where the change is made function as expected.

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Problem Cause

Known issue [CVADHELP-18694]

https://docs.citrix.com/en-us/citrix-virtual-apps-desktops/1912-ltsr/whats-new/cumulative-update-5/fixed-issues.html