In May 2020 I purchased the Decklink Quad HDMI for use with my AMD Threadripper 1920X. After several rounds of tech support emails Blackmagic Design issued an RMA. A month later it was returned with a clean bill of health. A month after that tech support discovered an issue with the Quad HDMI and AMD sTRX4 systems.
That was six months ago and there is still no mention of the potential incompatibility on the Blackmagic website or support documentation.
Note: OBS is used to demonstrate the issue but it affects Media Express as well.