I used Google Maps navigation for times without any problem, on several different devices; currently I'm using a Google Pixel 3a, and it first worked properly too.
But suddenly, it began to cut EACH guidance phrase before the end, like in this example (freely translated from French):
In 200 meters, at the roundabout, take the (silent here)
This happened systematically during some days, after which it started working properly again.
But it started again cutting phrases some other days later!
This has occurred during months: working - not working - working - not working...
Till it totally stopped talking: visually the navigation process works fine, but now the device never says anything at all.
Obviously I controlled my configuration, which is correctly set to have the guidance playing.
Important precision: very strangely, this happens for car guidance, but pedestrian one talks normally!
I tried following numerous help pages from the net, without success: they all address either configuration settings or device malfunction, so the proposed solution always concerns a general problem (affecting any sound usage, at least inside of Google Maps), while my problem clearly happens for only certain parts.