I'm having a problem on iOS : I use the Force Background option in order to keep the app active and to receive calls while it is in background, however, as soon as I activate it, I cannot record videos using the iPhone Camera app anymore.
If I close the app by clicking once on the home button, the problem is still there.
If I close the app completely by clicking the home button twice and sliding the app up, the video mode starts working again, but then, I'm not connected anymore so I can't receive calls.
If I disable Force Background, I can once again record videos, but do not receive my calls anymore while the app is in background.
I tried uninstalling/reinstalling the app, but did not solved anything.
My config : iPhone 6, iOS 9.3.5, Zoiper 3.9.0
Could reproduce the same problem with an iPhone 6S, iOS 9.3.5 and then 10.0.1, Zoiper 3.9.0