I created following event:

class EventX implements Serializable {
  private BareJID userJid;
  private HashSet<String> enabled;

  public EventX() {}

  public EventX(BareJID userJid, HashSet<String> enabled) {
    this.userJid = userJid;
    this.enabled = enabled;
  }

  public Set<JID> getEnabled() {
    HashSet<JID> result = new HashSet<>();
    if (this.enabled != null) {
      for (String res : this.enabled) {
        result.add(JID.jidInstanceNS(userJid, res));
      }
    }
    return result;
  }
}

In as userJid I passed test@example.com and as resources [ test-1 ] on one cluster node and on second cluster node when I called getEnabled() method I received test@example.com/test@example.com/test-1 which was rather not expected.

I was able to solve this issue by changing method name to getEnabledJids() as serializer used getter method to collect values for field and serialized this collected value, which was not expected result and caused issue here - invalid JID.

Would it be possible to somehow deal with it on system level?