Polly: Errors after first start of the app

[ehrdi]

When starting the app for the first time and returning a "y" after the first joke, this Error appears:

ValidationException: This voice does not support the selected engine: standard
    at Object.extractError (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/aws-sdk/lib/protocol/json.js:51:27)
    at Request.extractError (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/aws-sdk/lib/protocol/rest_json.js:55:8)
    at Request.callListeners (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/aws-sdk/lib/sequential_executor.js:106:20)
    at Request.emit (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/aws-sdk/lib/sequential_executor.js:78:10)
    at Request.emit (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/aws-sdk/lib/request.js:688:14)
    at Request.transition (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/aws-sdk/lib/request.js:22:10)
    at AcceptorStateMachine.runTo (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/aws-sdk/lib/state_machine.js:14:12)
    at /Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/aws-sdk/lib/state_machine.js:26:10
    at Request.<anonymous> (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/aws-sdk/lib/request.js:38:9)
    at Request.<anonymous> (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/aws-sdk/lib/request.js:690:12) {
  message: 'This voice does not support the selected engine: standard',
  code: 'ValidationException',
  time: 2020-09-09T08:44:36.468Z,
  requestId: 'e1673744-ebbf-440d-bea4-92c430865a3d',
  statusCode: 400,
  retryable: false,
  retryDelay: 43.58697214445122
}

after that, every 2nd time aws polly tries to read a joke this error gets thrown:

Error: No audio file specified
    at Play.play (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/node_modules/play-sound/index.js:31:28)
    at /Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/src/index.ts:88:16
    at step (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/src/index.ts:52:23)
    at Object.next (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/src/index.ts:33:53)
    at fulfilled (/Users/dirkehrhardt/Documents/ai/aws-ai-playground/packages/polly/src/index.ts:24:58)
    at processTicksAndRejections (internal/process/task_queues.js:97:5)