After spending hours I found the fix finally. I am using Lenovo Vibe Shot and my screen used to get all black while WhatsApp call and WhatsApp Voice message. Yes, it was proximity sensor issue, and the solution was to disable it. I disabled it from system settings but didn't work. Installed several softwares but just one software worked. And that is "Stay Alive". After installing go to Enable Selected Apps from Exceptions to Stay Alive. And that's it. No need to root the device either. Please let me know guys if this solved your problem. I just created my account to share my solution here. Hope it helps
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Sorry guys, even "Stay Alive" didn't work. So I read somewhere about Proximity Calibration. From dial pad I dialled ####1111# and it took me to all sensors test menu. From here I calibrated my Proximity Sensor and it works well
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