Quoted from Indusguys:
mshonbrun do you have any idea why my optos seem to be misaligned/ not registering?
This happened to me on Scared Stiff skill shot scoop. When switching in a new opto change both the emmitter and receiver. I swapped in just the side that emmits the light and she worked for a week or so and then kept failing. I thought I had a bad solder joint and went back to resoldering in another emmitter. Stll didn't work and now I checked other switches associated with this set of optos on the switch matrix. Everything checked out ok so I went back to the initial culprit. I plugged in the set and held her in hand and tested her with my finger running between both to break the beam. She registered perfectly until I screwed the set of optos on either side of the vuk. Once back in place the optos were too far apart to read the light. When I tested them in my hand they were closer together and registered. Once I noticed this I called my friend Dennis and he told me to get in the habit of changing both optos as a set. I soldered in a new receiver and she was able to see the beam and when it gets interrupted. Hope this is what you're experiencing.