Autonomous only works 3 times after download

[Imprudent]

Hello,

In the course of my programming the VEX robot microcontroller, I have developed 4 different autonomous modes. In the modes, I use a combination of 2 encoders, 1 sonar sensor, 2 potentiometers and 5 line followers.

When I download the code, it will function perfectly for the first 3 trials but then it will start doing very strange things (ie; not turn, not move backwards, not stop moving backwards).

Has anyone else experienced this problem? If so, how did you fix it?
I realize that I could simply re-download the code before each match in Dallas but this will get rather frustrating and one more thing that we need to remember to do. Especially when we are in a rush or have other problems (usually mechanical) to deal with.

Thanks!

- Jenn