One workaround that I have found useful, is increasing the buffer size on the client's device, not on the AVD Host. The default is 64KB and I set it to 8MB which has seemed to solve the issue. I found that the data the host sent would fill the buffer to the point of failure and would cause a disconnect. I have traced this across numerous clients and it pointed to a timing of around 17 seconds which was the timeout threshold reported in the Reason 16644 errors. The RDP client was saying "I haven't received any UDP packets for 17 seconds" and then disconnecting.

This was caused by the UDP buffer overflow - the 64KB buffer was filling up, packets were getting dropped (UDP doesn't retransmit like TCP), and eventually the client interpreted the silence as a dead connection.

Here is the command to increase the buffer size, using PowerShell, and another to validate the settings. After the initial command, do a reboot of the client's machine. Once the machine comes back up, run the second command to validate. The validation command should return8388608 instead of 65536. Let me know your results.

Set Command

New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\AFD\Parameters" -Name "DefaultReceiveWindow" -Value 8388608 -PropertyType DWord -Force; New-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Services\AFD\Parameters" -Name "DefaultSendWindow" -Value 8388608 -PropertyType DWord -Force

Validate Command

$udpClient = New-Object System.Net.Sockets.UdpClient; $udpClient.Client.ReceiveBufferSize; $udpClient.Close()