I have the weirdness issue. I run IOS version 12.4 on iPhone X, and Zoiper 3.21.1, been using it since mid 2018, and it been working fine ever since two days ago.
Mind you, I also have this running on my Android, and does not have this issue I am about to described.
The App Register fine to the server and can make extension calls fine on the server. However, there are a few landlines numbers which I been calling since I have the app; when I dial these numbers the app just closes, when I dial numbers that I have never dial before the call goes through and the app never crash, which I find is weird.
As stated above, Zoiper on the Android never does this, running on the same server.
Can anyone tell me how to solve this please?