I have tried using a scanned photo jpg, scanned photo tif and camera generated raw file. I've had preferences set with and without "Use GPU processor" checked. In all cases, when I run Enhance the resulting file has several horizontal band where the pixels are missing. My machine summary is as follows. I've also attached a snippet of the problem.
Operating System Windows 10 Pro 64-bit CPU Intel Core i7 6700K @ 4.00GHz 32 °C Skylake 14nm Technology RAM 32.0GB Dual-Channel Unknown @ 1075MHz (15-15-15-36) Motherboard ASRock Z170 Extreme7+ (CPUSocket) 40 °C Graphics BenQ SW2700 (2560x1440@59Hz) PA278QV (2560x1440@59Hz) Intel HD Graphics 530 (ASRock)