I forgot a G3L CP gearbox is a grease lubricated box. So the kick start bump rubber won't have any oil to move it around. Unless it's a 1948 and later when they switched to oil.

Then I am still guessing it is the zinc spring box.

I'm thinking I'll just take it apart carefully and see where there is any wear or broken parts. Worst thing is that they are so messy being grease lubricated ! I'll post up what I find, it may take a while as we have other projects in front. Thank you for your thoughts Bruce.