Echo cancellation on Xperia X

This is a problem that has been bugging me for years (literally) but I finally got around today to confirming it.
I have an Xperia X with a Love Mei super-rugged case. I find that when the phone is in the case and make calls using the phone’s speaker and mike then callers hear their own voice echoed back to them. If I remove the phone from the case (even during a call) the problem disappears. The reason is not hard to guess - the rigid case literally carries the sound from the speaker back to the mike. So I have just learned to live with it by using an external headset whenever possible.
But today while upgrading to Sailfish latest version ( I first decided to reinstall Android first to see if the problem happened with Android too and found that there was no echo at all. I then went and installed Sailfish (now a virgin installation) and tested again, and yes the problem had come back.
So my question is, can anyone suggest a way of making the echo cancellation work under Sailfish as it does under Android?