I have observed that happening especially when I use the stock camera app on my samsung M21. The tiny green dot appears when I open the app but does not settle itself on the upper right of the screen as it should until the camera app closes. It resolves by restarting the phone, but after a couple of days it happens again. This bug needs to be addressed as it can have security and private implications for users.
We acknowledge your query and apologize for the same. We request that you kindly visit the service center for a physical inspection of your device. You can locate your nearest service center with this given link: https://www.samsung.com/in/support/service-center/
