I use Android Auto and the recipient of my call says they hear themselves echo

This issue seems to be localized to just users of Android Auto and has been covered in multiple forum threads such as this one. I believe the issue stems from the fact that Android Auto uses bluetooth for audio calls and Apple CarPlay uses the lightning cable for both audio and video.

This may possibly a bug in software 3.4 as well. A possible remedy would be to update the module to a newer build (build 21098?) to see if that fixes it for you. We haven't confirmed a fix for this problem just yet. Another short term fix may be to tap the "privacy" button twice on the display; others have reported that this fixes the issue temporarily but it eventually comes back.

We'll update this support article as we have more information.