Confluence denies working and throws a Cluster Error when ran within a Virtual Host on Resin

Confluence denies working when deployed into a Resin 3.0.22 webserver and configuring it to be available under a virtual host.

The following error is thrown after zero to 4 clicks:

2007-02-15 18:36:00,076 FATAL [DefaultQuartzScheduler_Worker-0] [confluence.cluster.safety.ClusterPanicListener] handleEvent Fatal error in Confluence cluster: Database is being updated by an instance which is not part of the current cluster. You should check network connections between cluster nodes, especially multicast traffic.
2007-02-15 18:36:00,080 INFO [DefaultQuartzScheduler_Worker-0] [confluence.cluster.safety.ClusterPanicListener] handleEvent TangosolClusterInformation: 1171564413957, listening on 225.192.131.249:32365
2007-02-15 18:36:00,096 INFO [DefaultQuartzScheduler_Worker-0] [confluence.cluster.safety.ClusterPanicListener] handleEvent Shutting down Quartz scheduler
[18:36:09.800] resin-file: init
2007-02-15 18:36:30,023 FATAL [DefaultQuartzScheduler_Worker-9] [confluence.cluster.safety.ClusterPanicListener] handleEvent Fatal error in Confluence cluster: Database is being updated by an instance which is not part of the current cluster. You should check network connections between cluster nodes, especially multicast traffic.
2007-02-15 18:36:30,026 INFO [DefaultQuartzScheduler_Worker-9] [confluence.cluster.safety.ClusterPanicListener] handleEvent TangosolClusterInformation: 1171564483152, listening on 231.202.143.86:32365
2007-02-15 18:36:30,032 INFO [DefaultQuartzScheduler_Worker-9] [confluence.cluster.safety.ClusterPanicListener] handleEvent Shutting down Quartz scheduler

The virtual host is configured as shown here:

<host host-name="confluence.de.wazap.com" root-directory=".">
<web-app id="/" document-directory="webapps/confluence"/>
</host>

The same server contains a JIRA but located under a different virtual host. JIRA works fine either under a virtual host or under the default host. Confluence denies working until ALL virtual hosts have been removed. I also added the multicast route manually and checked the firewall settings. So I'm 100% sure that multicast is working well.