Approximately a month or two months ago many people started having issues with #espeak-ng on android. While using other than english voice it was constantly switching it-self back into english. I could not reproduce it because I'm running as google free phone as possible with @microg instead of Google play services. If you are experiencing the same thing just update Google Speech Services app. https://play.google.com/store/apps/details?id=com.google.android.tts thanks to hint discovered by Milan Rezen.