The maven-javadoc-plugin does not seem to work properly with java 11 compiler:

• Does not always resolve dependencies correctly
• Does not recognize some annotations (e.g. @Override)

Some, but not all, of these issues are resolved in latest javadoc plugin release. So, we should upgrade to latest release (3.2.0) and also set failOnError to false to prevent compile from failing due to these javadoc plugin issues.