I created my first scene!

An NPC goes from A to F (in the way, he stops several times in other Xmarkers: B, C, D and E, talking about the village). AT first the scene elapse well. But, oh gods!. When i modified some packages from F (for example) the NPC stoped at point B.

Trying to modified B, then NPC stops at C. And the story never ends.... When C was fine, then D was "broken" etc.

Is it normal? The scene clearly starts but the NPC stop walking in certain phases, and dont know why