Secondary DisplayPort monitor occasionally flashes black for about a second

I have a system with a GTX 970 and two Dell P2415q monitors attached by DisplayPort running in 3840x2160 at 60Hz. Every once in a while, the secondary monitor will flash black for about a second and then go back to the correct image. This always occurs to the secondary monitor. I have tried swapping monitors and cables and the problem always occurs on the secondary, which seems to eliminate a defective monitor as the cause of the problem. This occurs with both 355.06 and 355.11. I have attached the nvidia-bug-report log, but if there is any other information I can provide, please let me know.
nvidia-bug-report.log.gz (146 KB)