Rear Drum Troubles

I have just had the rear sprocket/brake drum and cush rubbers replaced after the previous one self destructed, the bearing had worked loose and with the axle tighened the drum could be moved by hand. This bearing was only two years old, having previously been replaced in the old sprocket after the shoe started scraping on the drum.

The shop that fitted the new drum told me they had to grind a little off one of the brake shoes to get clearance from the drum when fitted, which was a bit of a surprise.

After adjusting the chain recently i have a light scraping sound from within the drum again. Initially if i loosened the right hand axle nut it would stop scraping but i don't want to loosen things too much.

So any suggestions on how/how not to set up the rear?
I have had a look at the exploded parts pic and all seems to be present. Should the back of the drum be metal on metal with the hub, it seems that the cush rubbers hold things slightly apart here?

Any feedback appreciated

Are you sure the shimming of the stub/dummy axle is correct ? If these shims are not setup right, the brake drum can be pushed one way or the other too far & the brake shoes can be pushed against the brake plate. Check that the circlip that holds the dummy axle & double bearing in place has not "jumped" out of the housing also.

I am sure you will work it out by having a good look at it.