GoKawiilMicrosoft confirms August update causes CompatTelRunner crashes on Windows Server 2016
Microsoft has acknowledged that the August 2026 security update can cause 0xc0000409 errors tied to CompatTelRunner.exe on Windows Server 2016 machines running the Compatibility Appraiser telemetry service. The bug affects both physical hardware and virtual machines, including VMware and Azure deployments, generating repeated Application Error log entries under Event ID 1000.