There is a gotcha with using SLG movement and edges which relates to cache cost (a parameter in SLG movement).
The image above describes how a movement from tile [1,13] to [1,12] should yield a path that comes around. However if the cache cost parameter is set to Yes then it will refuse to yield a path at all.
Setting it to No will solve the issue.
Not sure what this is about, but noting it down for future reference.