For me help this forum is my one of my hobbies, CCTV is part of my profession, people on here give a great deal of time helping and for free we even give better support on Hikvision cameras than Hik themselves.
Given the facts posted, you can see you've some sort of interference possibly electrical that your system is seeing, if you have this installed at home do the process of elimination, turn off everything, unplug everything see if it clears. Ground the NVR and see what happens.
But don't come on here and complain about the level of free help you , that's just not on.