The problem was actually reduced by RHM but NR refused to use comparative data at this location.
The issue was that the step board actually overrode the platform coper by quite a margin. Doing the RHM actually reduced the risk of a hit (because you effectively jack the vertical overlap by 25mm) but it still showed a hefty foul on the clearance model so NR wouldn’t allow a RHM 165, despite it being safer than an original 165! An original 165 is cleared in the SA so NR said they could still run. Yes, you have to, at times, completely suspend all logic when it comes to dealing with NR and route clearance.
So the track had to be sorted, which is probably the best long term course of action anyway.