Amazon QnA Intent unexpected fails - help

I am interacting with an Amazon Lex bot that is using an AMAZON QnA intent with a Kendra index. I am testing it with a simple query, for example: What is <something here>?

The issue is that it sometimes fails and sometimes works WITH THE SAME QUESTION. Here are the jsons (I replaced some information with <> so no private data is shown.)

Working json response:

{
    "messages": [
     {
      "content": "<This output is working as expected>",
      "contentType": "PlainText"
     }
    ],
    "sessionState": {
     "dialogAction": {
      "type": "ElicitIntent"
     },
     "sessionAttributes": {},
     "originatingRequestId": "<originatingRequestId>"
    },
    "interpretations": [
     {
      "intent": {
       "name": "FallbackIntent",
       "slots": {}
      },
      "interpretationSource": "Lex"
     },
     {
      "nluConfidence": {
       "score": 0.74
      },
      "intent": {
       "name": "Greetings",
       "slots": {}
      },
      "interpretationSource": "Lex"
     },
     {
      "nluConfidence": {
       "score": 0.72
      },
      "intent": {
       "name": "RequestAccessLink",
       "slots": {}
      },
      "interpretationSource": "Lex"
     },
     {
      "nluConfidence": {
       "score": 0.68
      },
      "intent": {
       "name": "AccessToIntranet",
       "slots": {}
      },
      "interpretationSource": "Lex"
     },
     {
      "nluConfidence": {
       "score": 0.64
      },
      "intent": {
       "name": "CreateCriticalTicket",
       "slots": {
        "message_ticket": null
       }
      },
      "interpretationSource": "Lex"
     }
    ],
    "requestAttributes": {
     "x-amz-lex:qnA-search-response": "<working>",
     "x-amz-lex:qnA-search-response-source": "<working>"
    },
    "sessionId": "<sessionID>"
   }

Not working json response:

{
    "messages": [
     {
      "content": "<fallbackintent message>",
      "contentType": "PlainText"
     }
    ],
    "sessionState": {
     "dialogAction": {
      "type": "Close"
     },
     "intent": {
      "name": "FallbackIntent",
      "slots": {},
      "state": "ReadyForFulfillment",
      "confirmationState": "None"
     },
     "sessionAttributes": {},
     "originatingRequestId": "<originatingRequestId>"
    },
    "interpretations": [
     {
      "intent": {
       "name": "FallbackIntent",
       "slots": {},
       "state": "ReadyForFulfillment",
       "confirmationState": "None"
      },
      "interpretationSource": "Lex"
     },
     {
      "nluConfidence": {
       "score": 0.76
      },
      "intent": {
       "name": "Greetings",
       "slots": {}
      },
      "interpretationSource": "Lex"
     },
     {
      "nluConfidence": {
       "score": 0.75
      },
      "intent": {
       "name": "RequestAccessLink",
       "slots": {}
      },
      "interpretationSource": "Lex"
     },
     {
      "nluConfidence": {
       "score": 0.69
      },
      "intent": {
       "name": "AccessToIntranet",
       "slots": {}
      },
      "interpretationSource": "Lex"
     },
     {
      "nluConfidence": {
       "score": 0.64
      },
      "intent": {
       "name": "CreateCriticalTicket",
       "slots": {
        "message_ticket": null
       }
      },
      "interpretationSource": "Lex"
     }
    ],
    "sessionId": "<sessionId>"
   } 

Any ideas?