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[Solved] MacBook Pro 14″ M1 Max encountering External Display Flickering at High Refresh Rates after update (macOS Sequoia 15.1)

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Home › Forums › MacBook, iMac & macOS Lab › [Solved] MacBook Pro 14″ M1 Max encountering External Display Flickering at High Refresh Rates after update (macOS Sequoia 15.1)

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  • November 14, 2026 at 9:06 pm #12348
    Jonathan Smith
    Community Contributor
    Diagnostic Hardware Specs: MacBook Pro 14″ M1 Max | OS Version: macOS Sequoia 15.1 | Archive Source: Apple Support Community #256770112

    I am running into a persistent issue on my MacBook Pro 14″ M1 Max running macOS Sequoia 15.1.
    Whenever the machine encounters DSC compression and VRR handshake failure over USB-C DisplayPort, the following diagnostic log appears in Console:

    WindowServer: [com.apple.WindowServer:server] Display 0x9ab6 link training failure / DSC buffer renegotiation

    I verified that hardware connections are intact and tested across different power sources. What is the verified diagnostic procedure to permanently eliminate this symptom?

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    November 14, 2026 at 9:06 pm #12349
    Sandra Nguyen
    Community Contributor
    Apple Recommended / Verified Community Solution
    This canonical solution was verified and marked as solved in the Apple Support Community archive.

    Locking refresh rate to a fixed frequency, disabling Variable Refresh Rate (VRR), and regenerating WindowServer display plists.

    Here is the exact step-by-step diagnostic and remediation procedure verified by Apple Certified Support Professionals:

    1. In System Settings > Displays, set Refresh Rate to fixed 120Hz or 100Hz instead of Variable (VRR).
    2. Reset display preferences: 
      sudo rm -f /Library/Preferences/com.apple.windowserver.displays.plist
rm -f ~/Library/Preferences/ByHost/com.apple.windowserver.displays.*.plist
killall -9 WindowServer
    3. In monitor physical OSD menu, set DisplayPort mode to ‘DP 1.4 Standard’ without aggressive DSC overdrive.

    Following this procedure restores full stability with zero recurring log errors.

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