last_utterance not populating after text entry (most of time but not all the time)

In testing my flow, last_utterance is not populating and results in Unable to fetch response msg when utterance is 2 sentences, but seems to when it's just the first sentence. Recommendations to resolve or is anyone else experiencing this? (But when it does populate with the shorter utterance, it's not following No match path.) I'm getting nowhere fast.