Hi @Claude, I came to exactly the same conclusion.
My problem was very similar: my rules stopped working the moment I set a slot that influenced the conversation. Until then everything works fine.
In this post Felicia commented that if you use slots that influence the conversation, it is necessary to define rules with conditions for each of the possible cases. However, this solution does not seem very scalable, since as the number of slots grows, or as you use non-boolean slots, handling the rules with these conditions becomes impossible.
As you comment, omitting the initial value seems to make the problem go away. I don’t know if this is a bug or if it follows a logical behavior, but I think this part is underdocumented in rasa.
Thanks for the reply. I’m going to ask Felicia about it and I will update the post if I find more information.