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[Solved] How to fix External Display Flickering at High Refresh Rates caused by DSC compression and VRR handshake failure over USB-C DisplayPort on Mac mini M4 Pro

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Home › Forums › MacBook, iMac & macOS Lab › [Solved] How to fix External Display Flickering at High Refresh Rates caused by DSC compression and VRR handshake failure over USB-C DisplayPort on Mac mini M4 Pro

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  • November 14, 2026 at 5:10 pm #8710
    Nina Patel
    Apple Master (Lvl 10)
    Diagnostic Hardware Specs: Mac mini M4 Pro | OS Version: macOS Sonoma 14.7 | Archive Source: Apple Support Community #256893665

    I am running into a persistent issue on my Mac mini M4 Pro running macOS Sonoma 14.7.
    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 0xda91 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?

    Mac mini M4 Pro | macOS Sonoma 14.7
    Apple Discussions Contributor | "Verified Apple Diagnostics Archive"
    November 14, 2026 at 5:10 pm #8711
    Ethan Carter
    Apple Master (Lvl 10)
    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.

    Apple Certified Support Professional (ACSP)
    Cupertino, CA | "Precision Apple Diagnostics"
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