Using a Samsung LC43J892DKUXEN 43" monitor with a Vega 64. I am unable to set the display output to 3840x1200 @ 120Hz. At 100Hz the display behaves as expected, however at 120Hz the display will turn black briefly as if there is a power loss or as if the source input has changed. This will repeat maybe a couple of times every minute. I have tested using a ROG Strix RX VEGA64 OC edition and a Sapphire Radeon RX VEGA 64 Nitro+. I've tested on linux 5.5.2 and mesa 19.3.3, as well as on driver versions 19.9.3, 19.12.3, 19.7.5, 19.12.2, 20.1.1, and 20.2.1 on Windows. I submitted this issue to the AMD bug report a few weeks ago but haven't heard anything back from them, so I am submitting here as well. I had the monitor sent back to Samsung for testing. They used a STRIX GTX950 and had no issues. I have tried multiple DisplayPort cables including the one included with the monitor.