In your case, you'll have to remove some of the insulation from the area in question. Small particles of copper are going to be liberated in the process. Not a good thing to have floating around. Take the failsafe off the projector and work on it where you can control where the dust goes.

Finally, once you've taken a close look under there and verified that it really is (or isn't) the problem, fiddling with it while it's mounted on the projector isn't going to get you anywhere. It'll end up being a lot easier and more convenient to just take it off and work on it on the bench.

All that has been said about the cut traces on the circuit board can be true, but also, it is possible that the cue sensor itself can be at fault. It does happen, not often, but it does. Please try to swap the sensor itself with another unit if you can. As was mentioned above, all you have to do is remove the two little screws (#1 Phillips head) that hold the sensor (the black box thingy) to its shelf, and then pull it straight out to unplug it. If the trouble follows the sensor unit there is nothing you can do about it other than replace it. Electronic parts do sometimes shift in value. In cases like this we are pretty flexible about sending replacements out "just in case".

I would never attempt to do any kind of work on the board when it was still attatched to the unit. I just wanted to know if I could connect a small wire across a trace that I could actually physically see was open just to see if that would solve the problem. But I will not do that.