Swagger Dist Upgrading versions goes to PetStore Example Definition not the one passed in the URL

We have been using Swagger UI Dist for ages in our project version 3.17 (yes thats old), and we need to update to the latest Swagger UI Dist 4.12. Updating the distribution has gone fine and the right version is being used however we pass as part of the URL the url parameter to get the definition. According to the documentation 'configuration items passed as key/value pairs in the URL query string' and this has the highest priority so it should be using the the url passed but it's still using the PetStore definition. I realise the SwaggerUIBundle has this

window.ui = SwaggerUIBundle({
url: "https://petstore.swagger.io/v2/swagger.json",

but then the previous 3.17 version also had that in the index.html as far as I can tell the url I'm supplying isn't being put in the input box for the definition to be picked up. If I manually put the url in to the Input box at the top then my api definition shows up fine. It seems that the url isn't being used and connect like it should be.