On Tuesday, February 10, 2015 at 9:15:42 PM UTC-5, wrote in sci.electronics.repair:
"Of course switching the TV to the mono carrier did solve the
issue but for some reason that TV set did not want to store
the setting and after off-on it was in stereo again. "

If no other user settings are lost it was probably by
design. Automatic. **** like this is why I almost never
buy anything new.

Not to make anything sound as easy as pie, but trying to get one "special friend" or (always remembering a certain tech's name) at each supplier/retailer probably makes things easier if you "had" to buy new.

That way, "just he/she" is responsible at that company for whatever later goes wrong. But then again, all that takes relationship cultivating You know, people sometimes come and go.