OP showed a video an there was no “ flashing” on it, none that I could see, I only saw noise.
Mind you this is only visible to him when watching the LCD with the camera on and the lens covered... a rather extreme situation and a normal one to show noise, which he calls “sparks” there was no “ flashing" on the video .
If that is what you see this is not abnormal!
If you have some other problem this might have been caused by the repair but the white dots of noise when shooting in extreme low light or no light are absolutely normal.
