I recently discovered that some HV mos devices with non-swappable source/drain were defined as standard mos and so LVS was allowing the source/drains to be swappable.
After reading the documentation I discovered they should be defined as type LDDN instead of MN. After enabling this in the LVS deck the devices were extracted as subcircuits named LDDN.
The problem is the source needs to netlist several HV nmos symbols as subcircuits of type LDDN, but when the different NCF files point to the same model (LDDN) it gives an error and doesn't netlist. I'm sure this is a common requirement so any help would be appreciated.