Yeah sorry for the misunderstanding, it’s hard to explain quickly from a not native like me and not in front of the sim. I was trying to say that by default the plane put you in a +500 up or down when engaging it. The alt engage works well but the problem is the VS engage button that need to meet many requirements to not to put you in a -500 descent. If you simply want to climb at desired fpm without setting an alt is better to use the autopilot nose up reference than the vs engage button because it’s a bit bugged.