Same problem here. Everything was fine until i swapped 5700xt to this Sapphire 7800xt Pure and started to get BSODs once in a hour while using Photoshop. Single display, all Freesync (both display and software) stuff is turned off.
WhoCrashed dump report says: Bugcheck name: VIDEO_DXGKRNL_FATAL_ERROR, Driver or module in which error occurred: watchdog.sys (watchdog+0x3AD0), dxgkrnl.sys (dxgkrnl!TdrIsEnabled+0x5F40).
Tried DDU, AMD Cleanup utility, even reinstalling Win, nothing works. Also tried lowering max frequency to 90%, power draw -10, undervolting, turning auto windows driver update off.
Specs: Win10, Ryzen 5900x, 2x32gb Patriot Steel Viper 3200, Fractal Design Ion 850 Gold, Sapphire Radeon RX 7800XT Pure.