The MxAccess docs explicitly state OnWriteComplete always fires after Write().
The real cause is no Windows message pump in the headless service process to
marshal the COM callback. Fire-and-forget is safe for supervisory writes but
would miss secured/verified write rejections (errors 1012/1013).
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
