SharePoint list is not showing images from lookup column

I have a list which when people add a new item it pulls in an image from a library using a lookup column and json format.

For some reason it's suddenly stopped working even though i've not changed anything!

The JSON formatting is

{
"$schema": "https://developer.microsoft.com/json-schemas/sp/column-formatting.schema.json",
"elmType": "img",
"attributes": {
"src": "=@currentWeb + '/Praise Badges/' + @currentField"
},
"style": {
"width": "100px",
"height": "100px"
}
}

I don't know if it's the JSON or something Microsoft has changed in the background, but if anyone has any ideas it would be much appreciated!