I had similar happen on my Plus 8 and it turned out to be a shoe steady spring hold down cup washer that had poor registration and let the shoe break free locking the wheel up in my case. I don't think the rear brakes are that different to a 4 wheeler which the diagram is from. It was a real PITA levering off the drum with a bolster and lump hammer very gently so as not to damage the backplate. I don't have a puller that big.
It's the one you turn through 90 degrees to lock. Part of No8 on the diagram, good luck.
![[Linked Image]](https://www.tm-img.com/images/2019/09/30/rb.png)
