[Solved] Mac Studio M2 Ultra External Display Flickering at High Refresh Rates (macOS Sonoma 14.7) – Verified Troubleshooting

[Noah Snyder]

Diagnostic Hardware Specs: Mac Studio M2 Ultra | OS Version: macOS Sonoma 14.7 | Archive Source: Apple Support Community #256702625

I am running into a persistent issue on my Mac Studio M2 Ultra 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 0x2124 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?

iPad Pro 13″ M4 (Magic Keyboard + Cellular) | iPhone 15 Pro | Perth, AU

Digital Nomad & Travel Filmmaker | "Verified Apple Discussions Archive"

[Jeremy Fuchs]

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 Air 15″ M2 (16GB) | GoPro Hero 12 Black | Apple Watch Ultra 2 | Bristol, UK

Apple Certified Support Professional (ACSP) | Digital Nomad & Travel Filmmaker

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