yaml unmarshal errors while uploading ConcourseCI pipeline

Question

I tried to upload a ConcourseCI Pipeline to my Concourse Server using

fly -t <my_target> sp -p my_pip -c pipeline.yml -l creds.yml

But the upload terminates with the following error message:

fly -t local-docker sp -p siemens -c build/paas_ci_cd.yml -l config/credentials.yml
error: yaml: unmarshal errors:
  line 44: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 90: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 136: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 182: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 228: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 274: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 320: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 366: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 412: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 458: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 504: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 550: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 571: cannot unmarshal !!str `go-buil...` into []string
  line 597: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 643: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 689: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 735: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 781: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 827: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 873: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 919: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 965: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig
  line 1008: cannot unmarshal !!str `bosh up...` into atc.TaskRunConfig
  line 1032: cannot unmarshal !!str `bash he...` into atc.TaskRunConfig

I already pasted my pipeline.yml into a yaml validator without any error complains. The pipeline was generated using erb templates. The lines which produce the error messages show now indentation problems or missing variables.