Bad home theater sound?

I have connected my smart TV to a Samsung home theater system via HDMI.

For a long time I have had the problem when I e.g. Watching something on Netflix or a blu ray that the tone of the language is always so funny. Either the speech is suddenly very quiet or sounds very tinny or scratchy. I already tried everything in the settings but it doesn't get better. System is also up to date

That is extremely annoying…

Does anyone know the solution to the riddle?

I would try to swap the center speaker with one of the others in order to rule out a defect in the center. This is what we do first in the cinema when it sounds strange, to find out whether a chassis has torn or the power amplifier is defective.