Hi Csaba,
Yes , this is a bug of JavadocType check - please report an issue.
It should report violation on class declaration line not to its annotation (that is why Suppression does not work, as it expect violation below itself).
For the sake of simplicity please put to issue a minimized input file and config and prove violation by CLI, like:
18:39 $ java -jar checkstyle-6.11-all.jar -c checkstyle-checks.xml BackgroundExecutor.java
Starting audit...
/var/tmp/BackgroundExecutor.java:XXXXX: error: Missing a Javadoc comment.
.
thanks,
Roman Ivanov