Hi sbotez-bewhere-c,
Welcome to Community! Having the option to set default payment methods to your customer profiles, is just one of the many valuable features in QuickBooks Online. I can understand the impact, when you're not able to edit the default payment method. I would be happy to provide some insight here!
In this situation, I suggest clearing the cache on your browser, if you haven't done so already. If you have an excessive amount of frequently accessed page resources, it can cause unusual behavior. In addition, I recommend trying another browser such as Google Chrome, Safari, Edge, Firefox, or a private browser.
If the issue persists, please don't hesitate to contact us outside of Community. A member of our Customer Care team will look into this issue in more depth and escalated it for further investigation if needed.
Feel free to reach back out with other questions. We would be happy to help!
