No, nothing like that. Those are not permanent. And M20 display is LCD, not OLED. Sometimes you will see that some lights, after they are turned off, still emit a dim glow for a small amount of time, the same happens here. And it happens with every M20 device. It is temporary so nothing to worry about.
Oh sorry, I didn't knew that, I thought it might have OLED display like other Samsung devices. But still display burn in issue will stay forever, trust me before this I was using Mi A1 and one day this same issue started happening with my display, later on I reached out to Xiaomi on their forums and via mail to customer support, they asked me to visit a service centre and get it replaced.
Okay...but as this is not a serious issue and affecting all the devices just because it is LCD, I will visit service center in case I face any critical issues.
Wait, its there in your device too? Dude, screen burn in should never happen in an LCD screen it's not a common issue.
You can say that it's common for OLED because it is.. but not for LCD, that's a faulty display, you have paid money for that device, atleast get it checked while it's under warranty.
Please perform the following steps to resolve the issue:
1- Check the mentioned issue in safe mode.
2- If still issue persists, kindly visit nearest service center for physical inspection of your device. Service center personnel will provide you the further resolution. Follow the link mentioned below- http://www.samsung.com/in/support/servicelocation/
