This is caused by UDP not working correctly. The solution is to turn of UDP for the RDP client. This problem may occur on some machines and not others even using the same VPN connection from the same remote site and each configured the same. There is a group policy setting to turn off UDP in RDP. However, it has no effect on the problem on the machines I’ve tested; it apparently works for some people but not all. To fix the problem, a registry edit was necessary. From command line as administrator or PowerShell as administrator run the following
REG ADD “HKLM\software\policies\microsoft\windows nt\Terminal Services\Client” /v fClientDisableUDP /d 1 /t REG_DWORD
Another setting that can affect quality of the image. In Remote Desktop > show options. On the experience tab, uncheck persistent bitmap caching. It helped to a small extent on freezing but did not cure the problem. However, the fact that it helped suggests this will improve performance.
The group policy setting that did not work for me, even after multiple reboots, but may for you. Computer Configuration > Administration Templates > Windows Components > Remote Desktop Services > Remote Desktop Connection Client. Double click the setting “Turn Off UDP On Client”. Choose Enabled option to enable this setting. Click Apply to apply the change.
The set of modifications for Windows 10/11 native VPN client to work are summarized at: https://jmwoccassionalnotes.blog/2022/10/09/configure-win10-11-client-for-native-vpn-connection/
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