I think the PMML Predictor-Node doesn't conform to the DMG PMML 4.2 specification(http://dmg.org/pmml/pmml-v4-2-1.html) anymore:
It requires Node IDs for Decision Tree Models even though these have been optional since PMML 3.0.
When I tried the Node on a .pmml file generated with spark-jpmml (https://github.com/jpmml/jpmml-sparkml), I got the following error:
ERROR PMML Predictor 2:2 Execute failed: Only numeric node ids are supported in KNIME. Found "null".
When I modified spark-jpmml to give each node an id it was working.
I think it would be worthwhile to correct this bug.