Phone echo when using CarPlay

I recently installed a Boss BE7ACP unit in my 2008 Toyota Solara. The unit has an external microphone current mounted on the driver's side window pillar. The unit has a USB connection for Apple CarPlay, but not a Bluetooth connection option. It has a Bluetooth connect directly to the phone (without CarPlay). The USB/CarPlay must be disconnected for Bluetooth to work/connect.

The phone is an iPhone 11 using iOS 14.7.1

When connected via CarPlay, there is an echo on the other end of the phone connection severe enough to make the phone unusable. This echo is present only when connected via CarPlay via USB. When connected via Bluetooth, the echo does not occur when making or receiving calls.

I have tried several remedies, moving components, trying to mute or adjust volume on the phone and the unit, but the echo has persisted.

This fault greatly reduces the effectiveness and value of CarPlay. Calls cannot be made or received f connected to CarPlay. CarPlay must be disconnected to make or receive calls.

This is a commonly experienced problem, based on questions and replies I have found in my search to resolve this issue. Furthermore, I have seen comments that the problem has only arisen when the iOS was updated to a more current version.

This issue should be addressed in future iOS updates. Apple has effectively made CarPlay unusable to a large segment of its customer base.