A moon anomaly? or a processing glitch?

I have an original copy of the Lunar Orbiter Photographic Atlas of the Moon and I can confirm that the white strip is there in the image. I can also tell from looking at it closely that it is a data glitch - it coincides exactly with the 'tramlines' running across the image that mark each strip on the photograph that was scanned by the probe before being transmitted back to Earth.

Many of the images have now been reproduced from the original tapes and the resulting quality is much improved, so the data may have been filled in from that.

One theory is that the shape is a result of progressive collapse of basaltic crater walls after impact.

The hexagon is usually formed when an expanding circle meets resistance from all sides (or, like at Saturn's north pole, the surroundings are pushing on the circle in the middle). It could be that, as an asteroid impacted the Moon to create that crater, the lunar rock was pushed outwards due to the force of the impact, and thus created this hexagonal shape due to the resistance of the surrounding rock.

There are many other craters on the Moon with vaguely hexagonal shape.