Extend release notes

docs/release-notes/12-1-3/README.md

@@ -13,6 +13,17 @@ Release date: 2022-05-12
 We released [OpenProject 12.1.3](https://community.openproject.com/versions/1550).
 The release contains several bug fixes and we recommend updating to the newest version.
 
+## Settings regression
+
+OpenProject introduced a larger refactoring of the app settings to clean up 
+the distinction between ENV settings and database-based settings.
+
+Unfortunately, that introduced some constraints that caused the following bugs in downstream products,
+warranting another patch level level release. We're sorry for the inconvenience caused.
+
+If you experience bugs in installing or using OpenProject, please help us by reporting them to our community.
+To read how to do this, please see [reporting a bug in OpenProject](https://www.openproject.org/docs/development/report-a-bug/).
+
 <!--more-->
 #### Bug fixes and changes