This is the optional extra Surprise Drive and it should be accompanied by the car making a sort 'Oh' sound! What a bizarre fault. No idea save to check the linkage on the selector assembly.
Many of these small cars have a axle transfer box which has a gear for forward and chain drive for reverse. A dog selector shuttles between.
Messerschmitt set, Goggo Darts, Heinkel 175, Fiat Jolly, Autobianchi, Fairthorpe Electron Minor, Borgward, Isuzu Trooper
Citroen BX 17TZD & GTI 16v
Held - MG Magnette ZB & 4/44
For sale - Vellam Isetta, Bamby, AC Type 70, Velorex, Church Pod, Reliant Mk5, KR200, Saab 96, Bellemy Trials, Citroen BXs