We are facing this issue after upgrading to 2.9.0. However, 2.8.7 continues to work fine for us.

Caused by: java.lang.ClassNotFoundException: com.fasterxml.jackson.annotation.JsonMerge
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at org.springframework.boot.loader.LaunchedURLClassLoader.loadClass(LaunchedURLClassLoader.java:94)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)