If the system remains stable through out the black screens and flickers, then check your cabling first. A faulty HDMI or displayport cable can cause a display to flash and flicker, especially at higher resolutions or while under a gaming load.
If the system locking up or crashing, then go through the steps in this article: https://xfxforce.zendesk.com/hc/en-us/articles/360045645393
If you feel you graphics card is the cause after troubleshooting, please register your graphics card and file a support ticket at https://support.xfxproducts.com/ , in the ticket describe the issue in detail and also provide what troubleshooting steps you have taken.