There were an error in the file SPJS-vLookup_frontend.js in the latest version 4.4.4.2 dated July 31, 2019 that made text fields prefilled when adding a child item show two times like “Text value, Text value”.

Download the package again from here and update the file found in /DFFS/plugins/SPJS-vLookup_frontend.js and ensure it shows as v2.2.135.

Sorry for the inconvenience,
Alexander