I think you've mixed up the original and the working files.
The problem is in the header line of the file:
This tells our importer to interpret the file as a 3D molecule, but the coordinates are missing for the third dimension, therefore the parity information is missing.
If you change this line to
then the stereo information is preserved.
I could not find this sdf file in ChemBl, all the downloaded files had the correct header line. Could you let us know how you've downloaded this file?