Some wifi users can't hear phone-in users on Jitsi Meet

We’ve been using Jitsi Meet for months with no problem, 6-8 people, some joining by wifi, others by phone. Now two new wifi users have come online, and they are unable to hear the people who are dialing in by phone. Other wifi users can hear them just fine. Any ideas?

Which browser is used by those that do not hear?

The first time it happened, I asked everyone to use Google Chrome, and I think they are all doing so, but it hasn’t helped.

Cause we had reports of people not hearing dial in participants when using Firefox or Safari, but I haven’t have time to look at it.