Camera robot project - servos only rotate in one direction

We have built the camera robot and are using the provided sample code. For some reason the servos will only rotate in one direction when the joystick is used. We've googled this and it seems to be a common issue but haven't worked out how to resolve it. I'm fairly sure it is all wired up as per the project instructions so am not sure where to go.

This is the project: CTC 101 (arduino.cc)

Please post your code, in code tags, and a schematic.

Sadly, that page requires an activation code so I can't see it.

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