Does the QR Code change in MS Forms?

This was a query from a Customer and I can find nothing online about this behaviour. Just to be clear, this is not the Collaborate link, this is the URL and QR Code generated under 'Send and Collect Responses'. I cannot figure out why this has changed. 

The Customer has 23 Forms and 22 have changed. If a change is made to the Form, does the system think the Form is a 'new firm' and change the URL? That seems odd to me when dealing with publicly shared URL's / QR Codes in documentation and customer correspondence. 

Is anyone able to shed any light on this? The Customer is understandably nervous about using Forms in this way if the Code will change without warning.