Some findbugs violations have been missing in previous versions (see SONAR-1666). A consequence is that some rules can generate more violations on the same codebase.
The profile "Sonar way with Findbugs" includes new rules (see SONAR-1534). Projects using this profile can have much more violations for the same codebase.
The rule CloneMethodMustImplementCloneable was badly configured, so it has never been executed (see SONAR-1805). This rule is activated in the profile "Sonar way", so some projects can have some new violations with the same codebase.
Some member variables, for example loggers, are now excluded from LCOM4 (see SONAR-1641). This metric can vary on some classes compared to previous versions.
Not compatible plugins
Plugins Rules Meter and Web (version 0.1 only) are not compatible. They must be uninstalled before starting Sonar. Delete the files from /extensions/plugins/.