https://18xx.games/game/111675?action=233

SR2 was triggered when no companies had bought a 2 train for an entire round. The remaining 2 trains were removed and the SR started. At the end of the SR, play presumably returned to the train buying phase of the currently acting company (the BCR). As the BCR couldn't afford a train, play moved to the next company. It looked to me like a bug, because play seemed not to have returned to the active company. A log message would explain the flow of play.
E.g. "BCR passes buying train (not enough cash)".