Problem with Alps Door Robot

[MetalRobotHead]

I have an Alps Door Robot which has a problem with the centre shaft in the dome dropping down and out of engagement with the two small rotating scanners each side, so they do not rotate when in action. On opening the robot found the centre shaft had dropped through what looks like a keyhole and into the gear box, the keyhole looks far too big for the shaft to lock onto, almost looks like something has broken off the shaft. I'm assuming it should somehow lock into the keyhole but how is a puzzle to me. I can see remnants of solder near the keyhole, however due to problems with soldering in that position I am almost tempted to use epoxy to glue the shaft into position.

Please see the three photos one with shaft too low in dome, two more with the shaft raised the other in the keyhole.

Any advice on how the shaft should be located would be appreciated.