Alexa stops speaking my output in between

Question

I am developing an alexa custom skill using NodeJs. I created interaction model Intents and handled it in code. My handler returning out as follows.

...

return handlerInput.responseBuilder
            .speak(outputSpeech)
            .getResponse();
...

Where outputSpeech is bit long string, about 550 characters, Alexa starts speaking outputSpeech but in between some noise occurred and alexa stopped speaking. I search about maximum characters length here, Answer here says that maximum character limit is 8k but my outputSpeech is just about 500-600 characters. What could be the issue? Is it maximum character limit issue or could be something else?

Any idea or direction would be appreciated, Thank you