System specs? Including make/model of your power supply
What motherboard are you running and is your BIOS up to date?
Did you run DDU (display driver uninstaller) and remove all past AMD/Nvidia GPU drivers .. reboot .. and THEN install latest drivers from AMD's website?
Are you running the latest chipset drivers from either AMD or Intel's websites?
Are you running separate power cables to each power input on your 6900xt?
Is your Windows install up to date?
Have you looked at your system Event Viewer for logged errors and see if it's pointing to some hardware/software issues on your setup .. ?
How full are your system drives?