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[Solved] Mac Studio M2 Ultra 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] Mac Studio M2 Ultra encountering External Display Flickering at High Refresh Rates after update (macOS Sequoia 15.1)

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  • November 14, 2026 at 11:07 pm #14193
    Alan Morris
    Community Contributor
    Diagnostic Hardware Specs: Mac Studio M2 Ultra | OS Version: macOS Sequoia 15.1 | Archive Source: Apple Support Community #256027543

    I am running into a persistent issue on my Mac Studio M2 Ultra 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 0x9802 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?

    MacBook Pro 16″ M3 Max (64GB) | Tether Tools Pro | SanDisk Extreme Pro 4TB | Oslo, NO
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    November 14, 2026 at 11:07 pm #14194
    Felix Chen
    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.

    MacBook Pro 14″ M4 Pro (48GB) | iPhone 15 Pro | iPad Air M2 | San Jose, CA
    Apple Certified Support Professional (ACSP) | iOS / Swift Engineer
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