Thanks for all the input. Combined region now compiles successfully. There remains one issue and that is when I use sorting (graph.do_sort), the compilation ends up with error
Exception in thread "main" java.lang.AssertionError: The turn cost storage must be initialized only once.
at com.graphhopper.storage.TurnCostExtension.init(TurnCostExtension.java:60)
at com.graphhopper.storage.BaseGraph.<init>(BaseGraph.java:144)
at com.graphhopper.storage.GraphHopperStorage.<init>(GraphHopperStorage.java:83)
at com.graphhopper.util.GHUtility.newStorage(GHUtility.java:281)
at com.graphhopper.GraphHopper.postProcessing(GraphHopper.java:854)
at com.graphhopper.GraphHopper.process(GraphHopper.java:671)
at com.graphhopper.GraphHopper.importOrLoad(GraphHopper.java:640)
at com.graphhopper.tools.Import.main(Import.java:50)
If I turn off turncosts for calculation, the sorted data compile, so the two features probably cannot be used concurrently