In fabric8v1, where we use pax-web 4.2.7, we've seen strange HTTP 404 errors after several restarts of bundles.
Further investigation revealed:
where hawtio-web bundle simply failed. Restarting of bundle didn't help, because the related org.ops4j.pax.web.extender.war.internal.model.WebApp was still hanging inside org.ops4j.pax.web.extender.war.internal.WebObserver#contexts's queue.
We've seen this in logs:
This NPE prevents proper undeployment of webapp.