Probably the drive belt is needing tightening. They do need to run quite tight and once adjusted the rear wheel spindle needs done up pretty damn tight to keep the wheel where it should be and to keep the belt tight.
And welcome to the strange world of there daft little cars!
Ah you see! Never dealt with belts or bevel boxes! So are you saying the belt may be slipping and sending a shock to the bevel box making it buck into the chassis? That would be a wonderfully simple and easy to fix issue then. Comforting!
🤞🏻
Thanks
