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On a query in the Samsung community, there was an issue asked about white horizontal lines appearing on the screen when using the camera for video calls. On the problem’s regard, the community manager said that this is due to a display-related compatibility issue with the S.LSI chipset.
To fix these phenomena you can change the screen resolution other than QHD+ in the display setting.
Settings > Display > Screen resolution > Select between HD+ / FHD+
It’s also recommended to update to the latest software version if pops up on the screen