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macOS

External monitor flickers over USB-C after macOS update

troublesync_editorial
1mo ago
Performance
Environment

Environment

M2 MacBook Air on macOS Sequoia connected to a 4K Dell display through USB-C.

What happens

What happens

The display briefly goes black several times per hour at 60 Hz.

What I have tried

What I have tried

Replaced the cable and reset the monitor to factory defaults.

I would appreciate advice on how to identify the root cause without risking existing data or configuration.

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COMMUNITY RESPONSES

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1 reply
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cloudklara Answer
user
Posted 2w ago • 0 confirmations

I would test the likely cause before changing anything permanent.

Likely cause: The update renegotiated an unstable high-bandwidth color mode over the USB-C link.

What I would try: Disable high dynamic range, select a fixed 60 Hz mode and update the monitor firmware before testing another certified cable.

After the change, reproduce the original scenario rather than assuming the first successful test fixed it.

daviddata
user
Posted 2w ago

That explanation matches when the issue started. I will test the suggested change and check the logs again.

Showing 1 of 1 community responses
AI DIAGNOSTICS

Incident analysis

Updated 1mo ago• Trouble ID

Most likely causes

The update renegotiated an unstable high-bandwidth color mode over the USB-C link. 79%
A recent software, firmware or configuration change is exposing an existing compatibility issue. 35%

Summary

The reported behaviour is consistent with the update renegotiated an unstable high-bandwidth color mode over the USB-C link. The safest next step is to verify that hypothesis with a reversible test before making permanent configuration changes.

Suggested Fixes

Verify the likely cause
Disable high dynamic range, select a fixed 60 Hz mode and update the monitor firmware before testing another certified cable.
Validate and monitor
Reproduce the issue once after the change, review relevant logs or metrics, and keep a rollback path until the system has remained stable.

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