Hey there @Valentin_H,
This might require a bit more of a technical look, would you mind creating a private case and attaching your BPT logs from the %localappdata%\BuildPatchTool\Saved\Logs folder?
This will greatly aid us in seeing where any missed pieces might be. For ease of traceability, please mention this thread pointing you over so we don’t retread any steps 
You can create the private case here:
https://eoshelp.epicgames.com/s/?language=en_US