Discussion about Heroes I.

Dear Heroes 1 enthusiasts, I'm encountering what seems to be a bug while playing: if a hero with 15 movement points (increased by a Gargoyle, for example) receives, say, Orcs, and then I go back into the hero's menu, the movement points become 10. However, if I don't go into the menu after the transfer, the hero moves 15 squares. Has anyone else encountered this? Is this normal? I'm playing on Platinum difficulty, using Windows Vista.