I was upgrading some part of my rail network, then after a couple of game years I went back to the city I use as main rail hub in the map, and I discovered that all local city transit is gridlocked because appearently a small crowd of people started to cross a street that was a pivotal point in the entire city tram network, then forgot how to complete the task and stopped midway, blocking everything.
I can’t find the directory that contains the savegames, if someone can point it to me, I’ll post the savegame.