FP5: outgoing voice on calls doesn't work at first

I imported a Fairphone 5 to the US this week…bought it from Clove Technology (delivered in two days) and moved the T-Mobile SIM from my OnePlus 7 Pro over to it. When I first tried making a call, though, while I could hear what was being said on the other end of the call, my voice wasn’t getting through.

I figured out that if you mute and un-mute, then turn the speakerphone on and off, voice starts working. It’s nice that I was able to get it working, but is there something not being initialized properly?

The weird bit is that the initial behavior was repeated when I put /e/ (official stable image) on the phone this morning: outgoing voice didn’t work until mute and speakerphone were toggled again. Whatever is causing this is apparently in both the stock firmware and /e/.