https://wccftech.com/galaxy-s21-ultra-owners-facing-a-strange-battery-drain-issue/

Although the Galaxy S21 Ultra is one of the best phones money can buy, it happens to be suffering from a strange battery drain issue. This is not just isolated, as many users have reported that they are facing the issue. Surprisingly, the app that is causing this issue happens to be none other than the camera app, and it only happens when the phone is idle. However, the weirdness does not end here; the issue comes in when the phone is in your pocket, and you are walking around as it leads to the camera app waking the device every time there is motion detected.

Now, as far as the battery drain itself is concerned, it can range from mild to severe depending on the device. One user even reported a drain of over 21% over the course of seven hours and just 15 minutes of screen time. This is terrible, and what's worse is that the only way to figure out is by advanced monitoring apps as the regular battery stats monitor will not show you anything. You can use GSam Battery Monitor instead.