I have this problem: In one room, there is a walkable area maybe 150 on X but just 2 on Y. So it looks like a thin line. In the other room, walkable area looks the same. But if I click in any direction in the first room, my character is moving that direction (on walkable area). But if I do it in the second room, he does nothing. I have to click exactly on the walkable area (which is really thin) to make him move. Why is that?
It's generally recommended that you don't have walkable areas that thin, for pretty much this reason: they don't always work. Try making it thicker in the Y axis (I think the recommended minimum is 3 pixels thick).
I'm not sure why it works OK in one room but not another, except that thin walkable areas are unrelyable, not completely unuseable - so you might just've got lucky in the first room.
Is there really no way to do it? Im desperate! Now my character is moving OK in the first room, where the walkable area is 2 pixels thick, also in the second room, where the area is 3 pixels thick, but in the third room I must have a walkable area at least 4 pixels thick! Why?
My guess is it depends on the actual x- and y-coords. Walkable areas should be at least 3 pixels wide, so I think the pathfinding uses coords 0, 3, 6, 9 and so on.
Try going back to 2 pixels in the third room and move the line up or down by one pixel.
I think another factor is character's walking speed.
If the character is set to a higher speed, it would be more likely to cause problems when walking on thin areas.