Disregard – I have fixed it.
But to answer my own question for any others facing the same issue:
Rather than disassembling the whole unit to access the circuitboard, I taped a torch on top of the flywheel (beneath the handle) and after feeding the jack back in, gently prised the plastic guard back to make a gap between that and the flywheel. I could then guide the jack in place to the circuit board connector and with a metal skewer, gently pushed the jack up to click it back in place.
For such a simple issue, it seems crazy that access to this area has been made so difficult.