I have two or three Sony TVs of various vintages. All of them do this,
and I consider it a crappy human factors design element that Sony should
have gotten rid of years ago. I doubt there is anything you can do
about it, though.
By contrast, I have an old Magnavox el cheapo set. To change channels,
I just hit the number buttons. After each button, the TV waits a moment
to see if I am going to hit any more buttons, and if I don't, it goes to
the selected channel. In other words, if I just hit "5", it goes to
channel 5. If I hit "5" and then "7", it goes to channel 57. Etc.
Why expensive Sony's can't do this, I'll never know.
Bill