Hi all,
This is the first time I write here so I hope I understood correctly the passages above and possibly will provide this thread with some useful feedback. I use NAM 42 and had the same problem, concerning duplicated subway icons (in my case they were one after the other in the menu, so I couldn't fail to notice them).
I ran the SC4DataNode and realized that three Traffic Simulator Files, which were probably saved by the TSCT in the main folder of NAM, were overridden by files already present in NAM subfolders "5 DataView Options" and "9 Traffic Simulator" and that existed since the installation of NAM.
I removed the old files in the subfolders, and the double icon issue has disappeared, but I still have to verify whether this will also impact the traffic simulation (I assume that this will be the case, and that probably the custom traffic simulation I created never really worked as expected, since the relevant files were overridden).
Obi-Wan