[9.104] Teamviewer over HTTP-Proxy sometimes not working

Hello,

the teamviewer host software is installed on all machines in my network. I configured the firewall's IP as proxy server and entered the credentials of a user with no web surfing restrictions. Since UTM 9.1 Teamviewer is only working randomly. Sometimes it asks for a proxy user and password and refuses them, sometimes it says "Check your internet connection" and sometimes Teamviewer is working.

The following steps didn't improve the situation:

• Open 5938/tcp to the internet
• Creating a webfilter exception with the following content:
  
  Authentifizierung / Zwischenspeichern / Antivirus / Dateierweiterungen / MIME-Typ / URL-Filter / Inhaltsentfernung / SSL-Scan / Zertifikat-Vertrauensprüfung / Zertifikatsdatumsprüfung
  for URLs
  dyngate .com
  92.51.171.70
  ^http://.*/din.aspx.*DynGate.*
  ^http://.*/dout.aspx.*DynGate.*
  ^http.?://.*teamviewer.com.*
  ^http.?://.*teamviewer.de.*
• Adding and removing a valid proxy user from Teamviewer's configuration.

It seems that the requests are covered by the exception (see below) but the connection doesn't work.

2013:08:20-11:37:06 ASG-1 httpproxy[5792]: id="0001" severity="info" sys="SecureWeb" sub="http" name="http access" action="pass" method="CONNECT" srcip="192.168.1.18" dstip="178.77.120.6" user="" statuscode="200" cached="0" profile="REF_LFxaKhArSL (LDAP)" filteraction="REF_DefaultHTTPCFFAction (Default content filter action)" size="631" request="0x14778968" url="https://master1.teamviewer.com/" exceptions="av,auth,content,url,ssl,certcheck,cert date,mime,cache,fileextension" error=""


If I create an exception with the PC's IP it works without any problems.

Can anyone help me?

Cheers,
Marc