Nice job on getting the raycasts to work! Cool concept, thanks for still submitting it. Sometimes I can break the last object with only 2 lasers, its seems that the far right one counts as 2 if you wiggle it around a bit :)
Thanks for finding that bug! Using raycasts like this was a new adventure for me, so I was certain there would be some issues with the implementation. I will look into this particular bug so I can squash it next time I need to use raycasts in a similar manner.
Edit: The bug happens only when moving a laser from the focus lens directly to a mirror in one physics tick. The laser power on the lens is normally reduced when the laser is moved away, but I didn't account for moving the laser directly from one receiver (lens) to another (mirror). So, the laser power keeps adding up if you position the bottom mirror such that you can wiggle the right-most mirror to move the third beam directly to the bottom mirror or lens without hitting a wall.