Target blocks appear to emit signals with significantly different timing or behavior in the negative X direction.

Should a target block be placed atop an upward-facing sticky piston, with redstone power applied via redstone dust eastward (+X) of it, and a westward-facing sticky piston be placed to the west of the target block: When the dust receives power, there is a chance that the piston to its side will fire - this seems to be position-dependent, as it is consistent for redstone placed at some particular location in the map, but seemingly random in general. The piston does not fire when the same is attempted rotated upon other axes.

Note that this is not true when used in combination with other components - repeaters, note blocks, lamps, etc. are all consistently powered when used in place of that piston.

A video of the phemonemon: https://www.youtube.com/watch?v=ptK-7n--yYM

In the linked video, notice that some of the westward-facing pistons (to the left of the view) fire when the lever is switched. The pattern of which are and are not fired is consistent. In all other directions, the pistons never fire.