When using power supply beams, salvage beams, power drain beams, and astromech, the beams will not hit the first target in their line of fire, and will instead hit the last one.
To test, line up a shot with two asteroids within the line of fire. Then, attempt to salvage from the first rock. You will find that you are mining from the asteroid behind it. More noticeable with planet mining.
This issue makes power supply beams on docked batteries useless, same issue is present.