Are you using CRU or AMD software to create the custom resolution? I think AMD software is broken for custom resolutions so you have to use CRU. Also, AMD doesn't accept EDID overrides for displays connected via MST Hub so make sure it's a direct connection. Last time I tried was a couple months ago.Last time I tried, YPbPr wasn't available for non-TV resolutions from my 5700xt. That's why I haven't been using the adapter haha.