no that's not an issue, even my galaxy S8+ has it, I have seen that in my iphone too, when you try to capture a bright illuminated object in a dark sky the another refracted image of the object from the lens also is captured, don't worry it happens in all phones with a bigger lens.
It is a spot Caused by the Reflection/Refraction of any object Like any Street light/Sun/ Moon etc...And you can avoid it by moving your Handset camera in such a way that it got mixed with the object itself..In day light it easy but in night time it is bit Complex.....
Please follow the below mentioned steps in order to resolve the issue:- 1) Clear the Cache of the camera (setting>>apps>>camera>>storage>>clear cache). 2) Do the reset settings of the camera (camera>>setting>>reset setting). 3) Do the reset app preference (setting>>apps>>three dots on the right top>>reset app preferences). Then kindly restart the device and check the issue. For further assistance, register your concern in Samsung members app (click on “+“icon>send feedback>Error report/ Ask Questions).
