[Appium 1.6.4, Android 7, C#] - Appium hang until the incoming toast goes away

We are doing test on real Android phone. Key facts: Appium 1.6.4, Android 7, C#.

The test scenario is desktop version makes an app call to Android mobile phone version. Android version needs to accept the app call by clicking the [AcceptCall] button on the incoming call page. The incoming call page will show up and stay for about 30 seconds. after that, it will should another page.

We get stuck on accepting the incoming call. It looks like Appium got hang when the incoming call page shows up. Before and after the incoming call page, Appium finds elements very quickly.

Does anyone having similar problem? any suggestions? Thanks!