My HD 7790 (which is essentially a 260x) does the same thing. Very annoying.
Haven't been able to find a solution.
Tried different BIOSes, different drivers.
Believe it may be a faulty card, at least mine might be.
Ryzen R5 1600 @ 3.90GHz (1.35V - 1.337V SVI2 TFN) | NH-D14 | Asus Prime X370 Pro (0902) | GSkill 16GB F4-2800C15-8GVR @ 2933MHz (16-16-16-36-1T) | GTX 970 @ 1507-1978/ R9 390 @ 1140-1600 | 2 SSDs and 2 Mechanical drives | Rosewill Capstone 750M | NZXT Source 220 | Windows 10 Pro x64