With the October patch OCT 2020 PSU, Oracle has changed the internal JVM contained in the Oracle Database from version JDK 1.6 to JDK 1.7.
Unfortunately, a statically initialized field from a nested class was affected by the modified behavior of the Java runtime in version 1.7. An indication of this fatal behavior is when you try to use the ORA_SFTP package you will receive:
ERROR ORA-29532: Java call terminated by uncaught Java exception: java.lang.NoClassDefFoundError
ERROR ORA-29532: Java call terminated by uncaught Java exception: java.lang.ExceptionInInitializerError
The solution is to update your OraSFTP product to the latest version.