New cd63 / cd67 question

Where to start?
I have a lightly modded cd67se ( with opa 627 op amps) which I love.
Suffering skipping problems so I fitted a new vam-1201 laser from evil-pay.
Laser will not focus!:eek: (thinking duff new unit)
Picked up a working cd63se as donor unit.
Swapped complete CD reader unit from 63 to 67 (does not function)

Does anyone know
Are the ribbon cable connections the same?
(sockets on the two main boards are a different type)

Could I have cracked a pcb track somewhere?

All suggestions appreciated:)