@bassman this is a strange issue. There seems to be something going on with the “_merge” column. If I drop it from your file everything is OK. I can export it to parquet and bring it back to KNIME without problems. But if I try to keep it or just rename it the problems start.
When you check the data types of the columns it comes back with the type “Category” (instead of Object?). So this seems to be the issue. @ScottF / @Iris - maybe you can check if the Python to KNIME conversion does something special with this type of data.
(sorry for the rendering of the SVG - KNIME has promised to work on that)