Calculated Field Date Formatting

Hello,

I have a calculated date/time field which for the past year has been working without issue however recently the formatting has stopped working.

It should look like the below (and it does temporarily after changing the formula and changing it back)

but recently it reverts to look like 

Here's the JSON I used:

{

  "$schema": "https://developer.microsoft.com/json-schemas/sp/v2/column-formatting.schema.json",

  "elmType": "div",

  "debugMode": true,

  "txtContent": "@currentField",

  "style": {

    "padding": "0 5px",

    "background-color": "=if(@currentField < @now, '#ff0000', '#007d00')",

    "color": "#FFFFFF"

  }

}

Co-incidentally we also have an integrated PowerApps form with this Sharepoint list which when a form is submitted takes about 30 seconds to a minute to visually update in the list where before it was instant.

Does anyone have any idea what could be causing these issues?

Cheers,

Dan