This appears to be an artefact that occurs with silent shutter mode in some cases. Regular shooting mode doesn't have this problem. I've read about this but I don't know the cause.

I'm assuming that's a firmware bug rather than some actual optical effect (the lines are parallel rather than converging toward the light source).

I was going to reply that zooming in on pictures is a path that leads only to madness, but you’re right; that is messed up.

CCD Saturation and Blooming

http://hamamatsu.magnet.fsu.edu/articles/ccdsatandblooming.h...