Black Shadow on the screen

Hi @davidlynch94469

Without seeing what it looks like it sounds like there's a faulty LED (or LEDs) used for the backlighting of the screen.

The TV model you selected for your question is an edge lit TV i.e. LED backlight strips are on the edge of the screen and not across the screen.

Here's a video that shows how to replace the backlight strips for your model TV.

If it is only a few LEDs that have gone faulty it is better and easier to replace the entire strip rather than the individual LEDs as there may be a slight colour difference due to the age difference between the new and existing LEDs plus if some have failed then the others may not be that far behind in failing also.

Search online for UE50NU7455UXXC replacement LED strips to find suppliers that suit you best.