That was precisely the problem we had (and I was that random person, in our case). Like I said, went to Roll20 tech support and they basically gave up after some basic troubleshooting. (They claimed they'd look at the issue long-term, but that was months ago.)
So for us it would be one person and they'd log off and log back on, but then a different person would be unable to hear them, and so on. 3 tries later we gave up when someone mentioned they had a discord we could use and we've stuck with that since moving from 5e/Roll20 to PF2e/Foundry. It just makes things easier sticking with the voice solution that we were already familiar with.
Interesting, in our case it was either it worked for everyone but me, or it worked for me but not for everyone else. Tried a fair amount of troubleshooting on our own (changing browsers, changing voice settings, etc.) but didn't get anywhere. Then tried getting help from Roll20, which was useless.
You can draw squares/rectangles, circles, lines, and freehand elements, and put in text elements too. You can then select an individual element, and customise its colour, whether it has text or not, whether it is filled or not, etc. I think it's pretty nice. Granted, I've only been using it a little bit, but I want to experiment with it more. I think when combined with Tiles to represent more complicated elements such as stairs and stuff, it might really shine then.
I've seen some issues with discord, but in all those cases the person experiencing an issue just logged off and back on to resolve it. It's entirely possible I've just been lucky with discord. You're right though, it is nice to have a backup.
I've seen RPTools described differently, perhaps I was mistaken, but Map Tools is the VTT I was speaking of, and missing from Morris's list...
As far as I can tell, there's no specific tool built in to draw arcs or semi-circles.
