I have two different node types that act independent of each other. The are labeled :TS:Function and :TS:Type:Function.
In code they both have a method getParameters() that's associated with a :HAS_PARAMETER relation. However, in the two classes, two incompatible types are returned by that function.
Currently the algorithm seems to select the wrong class, which leads to an empty list, as the items are all filtered out, when getParameters is called. The graph on the other hand is constructed successfully. So, this error only occurs on data retrieval.