[Problem] Service Discovery not working after upgrade

After upgrading to 0.5 service discovery (SD) GUI controls were moved to System -> Network -> Service Discovery.
Before upgrade I had SMB and AFP activated for SD. After upgrade, all check boxes are unchecked and when I check one and try to apply the new configuration the following error message appears:

Error #2002:
exception 'OMVException' with message 'Invalid method parameter: id does not exist, and it is not an optional property.' in /usr/share/php/openmediavault/rpcservice.inc:150
Stack trace:
#0 /usr/share/openmediavault/engined/rpc/zeroconf.inc(109): OMVRpcServiceAbstract->validateMethodParams(Array, '{???? "type":"...')
#1 [internal function]: OMVRpcServiceZeroconf->set(Array, Array)
#2 /usr/share/php/openmediavault/rpcservice.inc(125): call_user_func_array(Array, Array)
#3 /usr/share/php/openmediavault/rpc.inc(62): OMVRpcServiceAbstract->callMethod('set', Array, Array)
#4 /usr/sbin/omv-engined(495): OMVRpc::exec('Zeroconf', 'set', Array, Array, 1)
#5 {main}

Right now I couldn't find anything on the forum, maybe one could point me in the right direction? Or is this one new and I should open a bug report?

I digged a little around trying to find a solution.
In /etc/avahi/services I (only) found four defined services: afp.service, rsync.service, smb.service and website.service.
I deleted those files and ran omv-mkconf avahi-daemon. Those four files were created, my web gui still shows all services as unchecked / deactivated for discovery.
But now I least my afp service is found by my OS X system. (SMB not, despite the fact that the smb service is also running and configured.)
So, something is working. But I still can't deactivate/active service discovery via web gui.

I'm not really sure how to reset the weg gui, kill the gui's chache are whatever is responsible for that display error.

PS: Meanwhile I updated to 0.5.30.

PPS:
The rsync.service file looks a little bit odd. I won't file a bug report for that right now because I don't know whether this only applies to my already ... faulty system or is a general bug. Can someone chech his/her rsync.service file and tell me if it looks like this?

<?xml version="1.0" standalone='no'?>
<!DOCTYPE service-group SYSTEM "avahi-service.dtd">
<service-group>
  <name replace-wildcards="yes">%h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync %h - Rsync</name>
  <service>
    <type>_rsync._tcp</type>
    <port>873</port>
  </service>
</service-group>