I'm having a problem I think has the same cause -- I tried to make the max depth adjustable via a slider, and the slider doesn't work even though my filter and underlying logic is completely correct. It appears to me that the refresh behavior of the $tidgraph widget is broken and it doesn't refresh itself when its parameters change for some reason. If I entirely close the tiddler and then re-open it after adjusting the slider, it's updated.
I imagine this would be fixable, but I can't find any source code that isn't minified -- anyone know where that could be found?