In taking apart a few Modern Vespa models over the years, I've seen the same issues with corrossion between a few of the bearings and the metal shaft that goes through them. This can get so bad you need a special tool nobody has miles from nowhere when you need to change a tire, or get the variator cover off, or if you decide to upgear the final drive. Here are Stainless Steel Bearings for those applications. I have used them all, and they work.
Here is the bearing that goes in the Variator Cover:
Here is the bearing that the rear axle goes through in the final drive
And this is the one that needs replacing the most, the bearing in the swingarm that the rear axle goes through. This is the one that gets locked on the most.