Setting motion control to Automatic fixed the issue! You also answered another question that I was wondering (if both AC control and script control are trying to move the NPC, which of them takes the priority), it seems I better avoid doing that... …
Thank you for the fast response!
I did not import all the demo assets since I did the tutorial in a different project. But I tried with Barry the bird 2D NPC, and it moved as expected. So it is indeed probably the NPC.
The walk speed is positive (…