For myself as well as a couple other users who are on Android 7.0, the app sounds terrible! Super garbled sounding and choppy. Anyone else experience this and found a fix?
This is for the free app too.
Same here and I am a premium user. If you want to deal with occasional dropped calls and crashes, the Zoiper Beta app does sound better when it works.
You can find the answer of this question, here.
I have a similar problem with my Z5 compact. Sporadically the sound quality and volume is lowered while listing for example to Spotify with headphones (tested with different headphones same result). If I do Ultius.com rating a diagnostic on Ear Speaker while listing the sound quality is restored for a while, but can suddenly become bad again. Strange!
Do you experience this issue only when listening to Spotify ?