I can't be sure you're looking at the same thing I am, but I would recommend studying a diagram or close-up picture of the Apollo 11 seismic experiment. Unlike the later ALSEP experiments that were nuclear powered, the Apollo 11 PSEP was powered by a pair of solar panels deployed on the east and west sides of the instrument. The east panel was tilted to the east to pick up the sun in the morning and the west panel was tilted westward to pick up the afternoon sun. Both would (to a lesser extent) pick up the sun at midday.
The brightness of artificial objects on the lunar surface varies radically with sun angle, as many (like solar panels) are specular reflectors (i.e., they have smooth, shiny surfaces that reflect much like mirrors even if they're not silvered). If the sun catches a panel at a certain angle, it may appear very bright while the other appears dark because it is both intrinsically dark and reflecting only dark lunar sky.
Note that while the LROC uses a 1-dimensional "pushbroom" imager, it is not necessarily looking straight down but may be rolled to the left or right to view a particular surface target. Since the LROC is in a polar orbit, the views it gives us of each Apollo site may be from the east or west. This can affect both its perspective of 3-D objects on the surface and the sun angles that give a specular reflection.
What you think is a "shadow" is probably just one of the two solar panels.