First, if you post your project you will get better help because the problem could be something not intuatively related to the code or path tiles.
For example, if your sprites collision bounds expand into the solid portions of the walls when it spawns, the pathfinding algorithm might have trouble finding a valid path. Or, if the bounding box can't fit around a specific bend, the pathfinding can struggle. Also, depending on the settings in the pathfinding behavior, the path might not be what you think it is. Differences between your cell size setting and your actual wall size can make the actual path smaller than you think.
If the paths worked previously and are broken now, you most likely changed one of the above settings.
You show your cell size as 20. Your tile size appears to be 32X32 but that is a guess from looking at the image. For a cell size of 20 to completely cover a tile size of 32X32, the cell would have to be 40 (or a 2X2 cell) completely cutting into the path. I would guess this is the problem but without actually having the project in hand, it is only a guess.
Try changing the cell size to 32 and see what that does.