here's a save where you can pick the hillsman promotion for the clubman situated in the north of the map.
That explains your issue but it's not a bug.
- A Clubman only has 1 move.
- Moving onto a Hill costs 2 moves.
- The Hillsman promotion divides that by 2 so it only costs 1 move.
- When a Clubman with the Hillsman promotion moves onto a Hill it consumes the single move that unit has.