It looks very much like something we would see if there was a pinprick-hole in the bellows of a folding film-camera so could there be a hole in the shell of the imaging chamber in your camera?

However, I have never seen anything like that in a digital camera.

Hello. I think the shutter is broken. I'll think about whether to replace it or buy another camera. Best regards.

D500 1.4/24G

Thanks Paco. 

I see this monstrous beings peaceful working day in, day out, without complain. They dominate the view silently. I'm attracted to them and always try to capture something here. They looked specially alive this day.
  I had my gear with me and went walking back home. It is a 30min stroll from work.
   Z9, 70-200 2.8 fl

   any input is always welcome.

Thank you again for the warm welcome to the floating people 

   John, thank you for the treat on cyclops and asahi super-takumar
   Daniel, that 58 neo-noct, specially the peacock, such  beautiful rendering


  Here, late evening alien's landing place
    Z9, 70-200 2.8 fl