What's causing the letters and characters to be incomplete, like for
instance, a "T" without the horizontal part or a "P" without its vertical
line?

It clears up and does great sometimes and I noticed it will sometimes clear
up after it has rested in a hot airplane for a while?

Yeah, it's an antique but I'm kind of attached to it. It has navigated well
over the years. Anybody got a suggestion about resurrecting it?