Custom remarkable markdown plugin only parsing first instance of matched regex

Question

I am trying to create a plugin using remarkable which will convert

%[callout]
{
    "type": "info",
    "heading": "LOL",
    "description": "qwrqwer!"
}
[/callout]

to a div showing the parsed json. Here is my code on code sandbox.

As you can see on the sandbox that it is showing a smiley emoji correctly if you paste the above code block in the textarea. But if you paste the same code multiple times it is only showing the emoji for only first instance of that code block and directly rendering the code block as a text for all subsequent occurences.

Any help would be appreciated.