In Back to the Future 2, Marty gets fired for doing something illegal. Several notes reading "you're fired!" were faxed to him. At the end of Back to the Future 3, Marty avoids the car crash and thus the words fade away.
Wouldn't it have faded away when 2015 Biff changed the timeline in 1955? Biff's changes meant that Marty never ended up working for Needles, so why didn't the note fade immediately?
Jennifer is the one with the "You're fired" note and she's not around (i.e. on camera) during the time from when they drop her off at her "home" in "Biff is Rich"-1985 up until Marty picks her up after the events in 1885.
Once they reversed Biffs changes to 1985, everything was back to the way it was when Doc & Marty visited 2015, which included Marty getting fired. When he changed his own future by not racing with Needles, the note turned blank.
Jennifer does not read the fax while in the alternate 1985 of the second film. Since that 1985 might very well not include a future where Marty is fired via fax, it should come up empty.
In a deleted scene from the second film we see Old Biff fading away as soon as he returns from 1955, since he has made his continued existence in 2015 impossible.
The fax should fade about that time, perhaps a little later as the disturbance in the timeline ripples out.
But after the events of the second and the third film, Marty and Jennifer are back in a timeline that mostly resembles the timeline at the end of the first film, where Marty is still poised to crash his car into the Rolls Royce. So the text on the fax will have faded back.
Only when he avoids that future by not racing do the letters fade.
