Video freezes often without activated camera

When I am starting a meeting with more than 2 persons that have their cam deactivated their video freezes. Mine as presenter works always fine. But when they activate their cam everything works fine again.

What is the problem and how can it be solved?

Everyone has a high speed connection.

I am telling them to activate the cam, but there are some meeting partners who do not want to activate their cam or they have no cam.