Most likely the back light is defective, eventually you can replace the faulty LEDs by yourself. Or the back light controller on an electronics board is faulty.
That´s why the dots of some back light LEDs are visible in your case
just an example (don´t know if these are compatible to yours), how your back light looks like behind the panel:
https://tvledbars.com/product/origi...j1-500tt25-500tt26-v4-v5-12pcs/?cn-reloaded=1