ZoneRefresh mixin returns always Block, even if the request is not a XHR request which leads to errors in the logfile.
This happens when crawlers load the URL with normal http GET request:
org.apache.tapestry5.ioc.util.UnknownValueException: A component event handler method returned the value <PlaceholderBlock>. Return type org.apache.tapestry5.internal.structure.ComponentPageElementImpl$PlaceholderBlock can not be handled.
Going to attach patch soon!