Liquid mapping inside a Azure function?

Question

Hi guys, so I'm hoping that you can help me out, I need to have my message liquid mapped inside an azure function, however passing the string version of my message which the beginning looks like this:

"{\r\n    \"originatingSystemID\": \"40792\",\r\n    \"regNo\": \"RE60 FEG\",\r\n    \"vin\": \"WDD2120022A371170\",\r\n...

The liquid map can't find the values that it needs to supply to the fields on the mapped message and ends up looking like this:

"{\r\n\t\"clientID\": \"DLRPRO\",\r\n\t\"originatingSystemID\": \"\",\r\n\t\"regNo\": \"\",\r\n\t\"vin\": \"\",....

This is the beginning of my liquid map for the above fields:

{
"clientID": "DLRPRO",
"originatingSystemID": "{<!-- -->{originatingSystemID}}",
"regNo": "{<!-- -->{regNo}}",
"vin": "{<!-- -->{vin}}",

I've been trying to correct it by converting the message to a JSON and then trying to use the root of that JSON as the input for the liquid mapping as the root of the JSON looks the same as the input I was using when creating the liquid map and also works when placing that root into this liquid mapping tool. (https://masterdatapoc.z6.web.core.windows.net/) However I receive conversion errors when I try that, the beginning of the root I've pasted below.

{
    "originatingSystemID": "40792",
    "regNo": "RE60 FEG",
    "vin": "WDD2120022A371170",

Can someone please help me out as I've been stuck on this all day :/

Thanks,
Kyle.