OH, that is something called WHITE CATCH.. And alas it is the broadcaster's fault. Not a lot you can do about it.
The other term for white catch is "Overmodulation"
I noticed that often back in the analog days of Teleision.. Alas, broadcast engineers do not take as much pride in their jobs as they used to.. I would never crank the wight up to 110 percent. Black yes, but never white (Blacker than black simply means no power is transmitted, but whiter than white makes trash)
Alas.. To explain farther I'd have go way too far into how TV works.
Home is where I park it!