I managed to start with all three routes accessible. When the time came to choose between them, I decided to follow Iris's route. To do so, I first told Luna I wanted to remain friends, then chose to keep the situation with Vaela unchanged.
This unlocked a scene between the protagonist and Vaela playing together. Iris then entered the bedroom to clarify the situation, and I reassured her by saying everyone else was just a friend, clearly committing to her route.
However, during the lunch scene afterward, Vaela still tried to interact with the protagonist, and I intentionally avoided further interaction with her to ensure focus on Iris again.
Later, when Vaela visited the protagonist's room for clarification, I chose the dialogue option "I thought we were just friends," which in this context clearly refers to Vaela. But somehow, the game misinterpreted this and the protagonist started talking as if it was Iris instead of Vaela, causing a confusing and unintended outcome.
This seems unintended or inconsistent with the context and player choices made. I've not pushed further investigation about the consequences of this.
I don't know if it's intended, considering Vaela can be a bit naive. After this dialogue, Vaela's event triggered first, and now Iris's event has started as well. It's both weird and amusing, but at least now it's reported.
Edit : Ok i got ejected from the ship :D