If you've added this to frame 101 for example, and added it along with the other actionscript on that frame, you have:

var origen_texte=texte._y;
var origen_texte2=texte._y;
var origen_cuadrat=cuadrat._y;
cuadrat._y = 85;
setProperty("texte", _y, "250");

Which is exactly the problem. The script is setting the variables used to calculate how much to move the textfield movieclip before it resets where the textfield movieclip should go. So you simply move the last line to the first:

setProperty("texte", _y, "250");
var origen_texte=texte._y;
var origen_texte2=texte._y;
var origen_cuadrat=cuadrat._y;
cuadrat._y = 85;

Fixed