Hi @nicogouin
Is there anything special about your VCF input file?
Things to check
- Datatype assigned to the dataset is vcf
- The file is actually uncompressed (your error leads me to think this might be the problem…meaning, the file is still compressed. Galaxy usually works with uncompressed VCF data, and this tool definitely does.)
- You can check the first two by “re-detecting” the datatype under the pencil icon → Edit attributes “Datatypes” tab. If the guess is not vcf there is a format problem.
- Then, does the RPBZ field exist in the file?
Run those checks and if you can’t solve the problem, I’d like to review for some potential server side issue. How to share your work:
- Troubleshooting resources for errors or unexpected results << general “how to check inputs”
- How to get faster help with your question << history share link is best for this one please
I’ll also try to find my older test and run that again to see if anything pops out. 
Thanks for the followup!