@Polux37 Thank you for your detailed analysis of what is happening. I've drawn your posting to the attention of the developers.
I agree, clear rules and no misleading information in-game about when bubbles will and won't drop would certainly be good and is what is expected. If they had said at the outset the bubbles will drop at various times in various locations without warnings on a move, then that would be clear. That isn't the case on FS15 from the start.