Apple Maps on iOS 15.2 does not provide audio turn-by-turn directions after the first turn

The details:

• iPhone model: 12 Pro
• iOS version: 15.2
• Not paired to vehicle's Bluetooth; strictly trying to listen to voice directly through phone.
• No Bluetooth devices (such as Power Beats Pro) are paired to the phone while driving.
• Siri Voice: British Voice 2.
• Siri Language: US. I don't use Siri, though, and mostly have it turned off.
• I'm not sure this makes a difference, since I compared it to a working iPhone that is set identically except uses Irish Voice 2 for Siri, but under General > Language & Region:
  • iPhone Language = English (UK)
  • Region = US
• I still get the wrist taps on my Apple Watch and navigation still otherwise works.

For the last few months, every time I have updated iOS, I would lose audio direction in Maps. Muting the audio then unmuting it through the Maps app (see image below, where it says "Turn off spoken directions.") after starting the route seemed to fix it most of the time; sometimes I had to restart the phone, and it would start to work again.

Now, after moving to iOS 15.2, I get nothing, unless I mute the sound via the sound controls within the Maps app as noted before, and then unmute it. Even then, it only announces the most recent step. The volume is REALLY low, even if I crank up the volume with the side volume button. If I swipe down from the top right corner to bring up the control center, I can raise the volume that way and it stays raised.

If I mute/unmute again and another step isn't imminent, it immediately repeats the most recent one.

I basically have to mute/unmute voice navigation every time a step approaches, and that is unfeasible while driving.

I have:

• Switched Siri voices to a different voice, quit Maps, then set it back to British Voice 2.
• Restarted my phone.
• Uninstalled and reinstalled Maps.

Obviously, nothing has fixed it. The language/Siri voice/region configuration described above has worked just fine through... iOS 13? I'm not sure when it started. I don't have Google Maps on my phone and I'd rather not.

I'm at a loss. Any further suggestions, or where to check for error messages, are welcome. Thanks in advance.