Windows 11 Insider Preview Feature Update (26220.9343) endet mit Fehlercode 0x800b0109

The code 0x800b0109 means a certificate chain ended at a root that Windows does not trust. It does not, by itself, identify a general installation problem or prove that build 26220.9343 is defective. Since you are upgrading from 26220.7872, record the exact update title and failure time before retrying. First verify the computer's date and time, restart, and run the Windows Update troubleshooter. If the error repeats, generate a readable WindowsUpdate.log with Get-WindowsUpdateLog and inspect certificate-chain failures in the CAPI2 Operational log around the same timestamp. Those details can identify what certificate or signed content is being rejected. Do not import certificates from forum attachments or disable signature verification to force installation. Submit the two build numbers, error, and relevant redacted logs through Feedback Hub. Without those logs, prescribing a particular certificate replacement would be unsafe and could address the wrong cause.