this is the reason you should send in you TX t be seviced every once and a while (say every 4-5 years) any radio has a tendancy to "drift" a bit. with modern and digital tech its less likely but still possible.

I know of at least one person whose TX started to splatter onto the channel below him and he says he was gonna send it in (im going to keep bugging him until I know he did) his TX is about 5 years old

I would rather pay a few buck every couple of years than risk shooting down someone becuase of a faulty radio.