Video conference performance drops

Question

If two devices on the network join a Zoom meeting, the video drops to about 5 fps and audio suffers just as poorly. 
 I can recreate the issue consistently and the issue only starts once the second device joins the meeting from LAN or WLAN and with multiple devices 
 
 Zoom Statistics say that there is 90%+ packet loss Sending & Receiving and warns that there is low bandwidth. 
 
 The Sophos is using less than 10Mbps for the video calls + normal network traffic (Max available Bandwidth 65Mbps Down & 10Mbps Up) 
 System Resource Usage is acceptable and never pins during this issue. 
 
 I have disabled IPS & UDP Flooding after noticing lots of UDP Flood logs but this did nothing.

What other logs or settings should I check to make sure its not a problem with the Sophos? 
 
 Thanks!

Winter7undra · Accepted Answer

Hey Paul, 
 The issue was two fold. The WAN MTU being too small and something on our ISP's end kept changing it back to a lower value. Because of other reasons we switched ISPs and the MTU remained at 1500 which fixed the issue. Hope that helps :)

sachingurung · Answer

Hi, 
 Did you check if there is an QoS configurations you are not aware about? 
 You can also check the total bandwidth that the UTM receives from the ISP by downloading a file via wget command. Alongside, look for any increase in dropped and error packets recorded on the interfaces by executing the " watch ifconfig " command in the shell. 
 Thanks,