++ FG100D Teamviewer / webradio streams freezing / stopping++

Hi guys, we are using a Fortigate 100D with Firmware v6.2.3 build1066. Currently we are facing problems with teamviewer and web radio streams.  Teamviewer sessions are working but are freezing for 10-20 seconds before the remote client (LAN or WAN) is responding again. Web radio streams are only running less than a minute. I created a policy with no filter except AV. Screenshots attached. Any idea where I have to look / how to find out where the issue comes from? Thank you very much and kind regards