How to deal with unreliable videoconferencing systems?
You should test all the equipment shortly before the meeting (but with enough time to fix things if there are problems).
It's a good idea (even if the system is working properly) to ask everyone to wear headphones to minimise audio feedback and to mute their microphone except when making a point (especially in larger meetings).
If you start a meeting knowing the systems are unreliable, you can ask everyone to minimise the use other applications during the meeting to boost performance. You could also try switching to audio only as that takes up less bandwidth.
If the problem is limited to one or two participants, you could ask them to leave the conference and arrange for them to be briefed/consulted once the meeting is over. However, you would need to defer any decisions/action points requiring their input until you've spoken to them.
If things deteriorate to a level where you can't have an effective meeting you should either try a different videoconferencing app or postpone the meeting until after any problems can be fixed.