Gilera runner help PLEASE

Hi I’m really lost and have no idea hopefully someone could point something out or help me

Between the side casing on the engine you have a rubber that stops the centre stand from touching the engine

All of a Sudden It keeps falling out iv replaced with new and 5 mins later it fell out

Iv removed the centre stand for now but would like to put it back sometime but without the rubber it vibrates really bad

Any ideas ??