Recently the notification_filters object was dropped from Account, and the way to change notifications for users and accounts was changed to a new endpoint. (See the change notes for Oct 8 https://beta.doc.bunq.com/basics/changelog) This breaks the way I use the API. I threw a few hours and the problem and now it's working again.
An API is a contract between you and numerous client programs. Rule #1 for public API's is that they are cast in stone. There is no right time to introduce breaking changes for your users. Any change, however small, that requires changing client code should be reserved for a version 2, with a new URL.
Why are you making breaking changes to the API?