I've been using Zoiper with an asterisk server for some days now and I have a rather annoying problem. The setup is on some android 6.0 phones with the latest zoiper app from the Play Store.The phone is connected through WiFi. When receiving an incoming call I have zoiper ringing and vibrating even when on call, and it keeps ringing after the call is completed indefinitely... which is very annoying. The only thing possible is to turn off and on my phone for this to work again. It something not occuring always, and I wasn't able to reproduce it. The phones are motorola moto E 4G.
Thank you and best regards