Having the same black lines appear when scrolling through the different backups in the timeline. A somewhat similar issue pops up sometimes when I had the Macbook with lid closed during the night, then open it in the morning and have weird artifacts on the screen. Sleep&Wake-cycling once fixes it, but absolutely less than ideal. I would assume, since it works without problems 95% of the time, that it is a driver-issue with the graphics?
Seeing the exact same problem with Time Machine on a Macbook Pro early 2013. Showing some other graphics problems (periodic black screen) so wonder if this is related to the GPU problem. Any have success fixing this?