the instructions say to set rod with no play.
This is the bit I don't get, but I'm no expert. With no play this will mean the brakes will apply very early on during the draw shaft travel, but maybe that's what should happen. If the front actuator lever which is attached the clevis pin and brake rod doesn't travel much during draw shaft travel, your trailer brakes may apply during the last few cms of draw shaft travel, which is correct.
Indespension when asked said that what should happen is brakes apply as soon as rods move
Assume you mean the steel threaded rod from the front actuator to the brake equaliser?
So that we are on the same page, here's my summary.
1/ Make sure the brake shoe expanders are the right way round.
2/ Adjust the brake shoes so they are just off the drum when towing.
3/ Tighten the brake rod to the front clevis.
4/ Adjust the rod at the equaliser to apply brakes during the last few cms of travel of the draw shaft whatever adjustment it takes to achieve this, i.e. when the draw shaft comes to a stop when pushed in.
Another suggestion, when you are reversing onto your drive are you able to pull forward by about half a metre to release the brakes? I'm thinking the trailing shoe may lock on (which becomes the leading shoe when reversing and the one I think should release).
The only other thing I can think of is that for some reason (and I can't actually think of a reason why) but by not having the front wheels on the ground during a reverse manoeuvre in order they release their brakes, possibly forces the rear wheel shoes to stay on. I think this may be a daft idea but then trailer brakes are a bit archaic.
I would love to come and help to see if we could trouble shoot this together but you're miles away, albeit in a beautiful part of the World.