Diagnosis
An intermittent connection in the wiring harness that runs through the folding hinge. The repeated folding fatigues the wires.
How to Fix It
Unfold the scooter and ensure it is fully locked. Locate the rubber cable boot on the side of the folding hinge. Gently pull the bundle of wires inside the boot slightly taut to remove slack. Then, carefully re-seat the boot. The connection is often restored by removing play in the cable.
If That Didn't Work
A wire within the harness has broken. This requires disassembling the stem to access the main wiring connector above the hinge and testing for continuity.
Heads Up
Avoid folding/unfolding the scooter excessively. When folding for transport, try not to let the stem hinge bear the full weight, as this strains the cables.