Modern Vespa

Hi, I've recently picked up a cheap old vespa ET2 non-runner, with the hope of a) getting it running and b) getting some experience of how it all works before purchasing something a bit more exciting!

I've made some progress, with a lot of help from this forum and youtube, but now I'm stuck 😬😬

I removed the rear brake cam and brake lever to give it a clean and stop it locking up, but now I cannot get it back in place!! There are two 'cogs' at the end of the cam.....one has gone through the lever, but the second one won't, so its stuck in the middle.....I can't get it to go in fully, or come back out.......any words of wisdom or tips greatly appreciated!!

the spline may be directional, there maybe some teeth missing so the arm will only go on the "right" way
Spin the cam 180 degrees & try again