Different information volumes: high and low

While navigating via car + Android Auto, the directions are given at different volumes inconsistently.
The first part of the instruction is given at a normal volume, while the second part is at a lower, non-adjustable volume.
For example: “IN 500 METERS” (spoken at normal volume) “turn right” is spoken at a low and sometimes imperceptible volume. I have not found a way to increase this volume.
This problem does not occur all the time. Sometimes both messages are at the same volume.

This does not happen through the app on the smartphone.

I have adjusted all the car and navigation settings, but without success.