See #288 for an example.

There should be a property, that is configured via commandline/ant/... to configure the tabsize.
It's currently at the default value of 8.
Note: At least the Designer needs to be adjusted, too - since it also has a special tab handling, which is currently 8.

If the tabsize doesn't match your editor configuration, then you might have trouble finding the reported violation position.

And consider setting the tabsize to 4 by default for all languages, since this is the most common setting nowadays.