MakerBot Replicator 2 home axis not homing

[dumbledad]

My MakerBot Replicator 2 is not working. There are two problems (perhaps unrelated). The main one is that the axis will not home, and the second (perhaps not even a problem) is that I found a stray plastic part on the base of my MakerBot and I'm not sure where it came from or even if it is part of the MakerBot!

I've posted pictures and video: https://www.flickr.com/photos/dumble...7647483786299/



You can see that the print head block moves towards the end but fails to touch the switch that turns off the drive; the switch itself is working (I can trigger it by touching it with a screwdriver) but there doesn't seem to be any part of the head that could ever reach it.

How should I fix the mechanism that stops the head drive when it homes?