Fastlane fails to upload dSYM files

Question

I have set up FastLane to build an app, upload to test flight, and upload dSYM files to Crashlytics. So, I can understand crashes. But, unfortunately on Crashlytics I always get a missing dSYM message.

This app has xx unprocessed crashes. Upload xx dSYM files to porocess them.

lane :buildTF do
    desc "Builds and uploads a version to TestFlight with what to test message"
    #cocoapods
    build_app(workspace: "NameOfProject.xcworkspace", scheme: "NameOfProjectScheme")
    upload_to_testflight(changelog: "Fix for the bug")
    upload_symbols_to_crashlytics
  end

Am I using it right?

Also, I have tried uploading dSYM files by using the script provided by FirebaseCrashlytics. It is located in the project folder /FirebaseCrashlytics/upload-symbols. I often get Segmentation fault: 11 Does anyone know how to solve that?