I have 9500HR Treadmill Lifefitness, Lift keeps increasing when pushing the down button.

Please see a handy diagnostic test mode guide here:

http://www.treadmillsrepair.co.uk/2014/07/diagnostic-test-modes.html

RUN the software calibration for easy diagnostic and fix it. Go under the HOOD motor, and follow the steps.
The Steps for Newer Style Console Calibration:

1. Locate the calibration area on the rear or underside of the console (a hole, near the console's center, that goes through to the electronics board. (This hole should not have a screw in it.)
2. Insert a pencil (eraser end), into the hole and feel around for the cal button (will click when pressed).
3. Press the button 2 times (with the pencil eraser). The first click should show CL11 in the console, the second click should show CL21.
4. If the process was done correctly, and CL21 appears in the console, you are in "calibration mode." The next few steps consists of pressing buttons on the console and observing settings. This will not require any other tools.
5. Press ENTER. CL22 should display in the TIME window and (??) in the SPEED window.
6. Press ENTER. CL23 should display in the TIME window and (??) in the SPEED window.
7. Press ENTER. CL24 should display in the TIME window and (??) in the SPEED window.
8. Press ENTER. CL25 should display in the TIME window and (??) in the SPEED window.
9. Press ENTER. CL26 should display in the TIME window. You should then see the letter "E."
10. Press ENTER. You should see "SS" or "55" in the console.
11. Push the STOP/START button. For safety, at this point, you should step off, or be off, the treadmill.
12. Push the ENTER button. The walking belt should start to move, accelerate to maximum speed, then stop on its own.
13. When the belt stops, the incline should self test by raising to its highest incline position, then lowering back down to its lowest position.
14. Once the incline test is complete, push the POWER button 2 times. The unit should shut off and the console should go completely blank. If this happens, the treadmill is done calibrating and is ready for use.