OK, here's my story.
One day, I noticed that the liveview of my D5200 started to exhibit a darker band/ stripe when exposing in low-light environment. Literally the right half of the screen appears darker.
I did my research and found nothing. (It seems I'm the only one in the world to whom this happened).
I conducted all possible tests: changing all possible photography-based settings (ISO, shutter speed, aperture), trying different lenses, setting the camera's video options to different ones (fps, PAL, NTSC, resolution 1080p 1080i).
Nothing answered my question: why does the half of my liveview appear darker in low light?
The pictures are artefact-free though! This default only appears on the liveview and affects the subsequent videos I shoot (as the videos are only shootable while on the liveview mode and not through the viewfinder).
When exposing in lighter environment, the defaults fades away and almost disappears completely. (Therefore also when augmenting the ISO or decreasing the aperture as well, but the problem remains when still shooting a less exposed zone)
I brought my camera to the Nikon repair service who claims the sensor had to be replaced and that the motherboard was fine after testing it. The camera being off its warranty and the cost of the repair being the price of the camera itself on the second-hand market (300€ vs 300€), I didn't let them replace it.
But how could it be a sensor-based issue, while all pictures I take are entirely default-free?
Here's a test: https://youtu.be/5qRbw846_xQ (25 fps - 1/50th | ISO 200 | f/2.5)
Any ideas? Thanks in advance!