If there is an error in a multiline command, deployer will not fail like bash-scripts do not fail unless the option "set -e -o pipefail" is used:

Example:

hosts:
  test:
    local: true

tasks:
  singleFail:
    - run: 'echo "Start"'
    - run: 'false'
    - run: 'echo "End"'
  multiNoFail:
    - run: |
        echo "Start"
        false
        echo "End 1"
  multiFail:
    - run: |
        set -e -o pipefail
        echo "Start"
        false
        echo "End 1"

dep -v single fails, because commands are executed one by one
dep -v multiNoFail does not fail, because errors in multiline scripts are ignored
dep -v multiFail fails, because with set it fails at any error

I would suggest to automatically add the set when there is a multiline command.