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Event ID 135: NtpClient was unable to set a manual peer to use as a time source because of duplicate error on '…'

Windows Event ID Lookup: What Windows event IDs mean: 4625, 4624, 4740, 6008, 41, 7045, 1102 and 3,000 more, with Windows' own message text, the fields and what to check.

Look up a Windows event ID from Event Viewer, a SIEM alert or a log export: what it means, the fields it records, and what to check. Many IDs are used by more than one source (event 41 is both a Kernel-Power crash and a boot error), so every definition is shown, the one people usually mean first. The message text is Windows' own, read from the event providers of Windows 10.0.26200.0, 2026-10-28; the notes are ours, based on Microsoft's security auditing reference.

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NtpClient was unable to set a manual peer to use as a time source because of duplicate error on '…'.

Event 135
Time-Service
System log
Warning
Message and fields (as Event Viewer shows them)
NtpClient was unable to set a manual peer to use as a time source because of duplicate error on '…'. The same time source '…' has been either specified as manual peer in NtpServer or selected as domain peer.  NtpClient will try again in … minutes and double the reattempt interval thereafter. The error was: …

Task Scheduler could not start task "…" because the machine was not idle.

Event 135
TaskScheduler
TaskScheduler/Operational log
Warning
Message and fields (as Event Viewer shows them)
Task Scheduler could not start task "…"  because the machine was not idle.