Problem in screensharing for more than 40 people

I use Jitsi meet on my own server for school classes.
when participants are less than 40 people, everything is fine. (Beside some bad quality sound once in a while, which i don’t know why).
But when more then 40 people join the meeting, screen sharing goes out and comes in over and over again.
I use Jitsi Meet on Ubuntu 18.04 LTS server, with 8GB or RAM and 6vCPUs.
When i monitored ram usage, about 6GB of ram was free when this problem occured.
and CPU usage was about 4%(Is it natural?)

What is the problem and how to solve it?

outgoing bandwidth

you mean the bandwith of server?

What is the optimal bandwidth for about 200 users?

Those bandwidth estimations are from 2015 and are without simulcast.

It’s a great document to start with, but I think they were also without lastN. So all bandwidth estimations have to take into account a lot of factors and it’s best to test in real life and adapt the server resources accordingly. You can never make a good enough guess in advance for the real usage, it will be very rough estimate.