Hi Kenelev,
By your description, I think might be your slowdown magnet on las floor bottom. Why? When you say, it always stop when's travelling to last floor bottom it need to detect first, the signal to slowdown before stop and that's not happen.
When you do re-learn, the only thing the car do, is recognise all the floors without recognise the points to change speed before arrive the floor to know how many floors exist on that hoistway.
I hope have helped.