You are using a URL button here. I am assuming that this close button is the finish button. When we use the URL button, then on clicking on finish, the flow will run again by default.
There is the following solution to this problem -
- You can define retURL in your URL to redirect. Reference
- You can create an action button and use flow in that action instead of the URL button.
- If you have a specific requirement to use the URL button only, then you can override the button behavior with the LWC component and
define your logic in LWC to navigate to your desired target.
- You can refer to this document if you want to override with the LWC - link