As an update, I went several times to the Samsung service centre, until they finally convinced me to factory reset the phone, which I was very hesitant to do. They believed that it was perhaps a conflict of apps and app data from when I first installed the phone. I was also having issues with the Google maps feature during WhatsApp calls. They suggested not to restore the old data and settings or else it could bring back the issue, but rather to install fresh copies of everything. After the reset, and carefully reinstalling my apps and data individually (which was painful), it seemed the phone was suddenly working much better that before, and the Google maps and WhatsApp screen issue seemed resolved. Until the next day, the screen turning off during WhatsApp calls issue began again. It was so upsetting after all that effort. However one interesting thing happened. While having the screen issue, I happened to be passing near the same Samsung service. So I took the phone in while the issue was occurring. The agent looked at the phone, removed the Samsung smart flip cover, and suddenly the problem was resolved. The screen timeout was normal during the WhatsApp call for that moment. It happened again just now, and again after removing the flip cover, the issue was resolved. I don't know if this is coincidence or whether the actual Samsung cover (perhaps a faulty chip) is the ultimate cause of these problems. I wonder if anyone else has had similar issues with these covers. I'm monitoring the phone now to see what happens next. This experience has turned me off buying a Samsung phone in future. I didn't pay so much money to have this prolonged issue that nobody can resolve. It's very disappointing.
