The folding Best Fitness BFT1 earned a rating of Don't Buy: Performance Problem because its incline feature malfunctioned on two of the three treadmills we tested. The incline controls on the first one stopped working completely shortly after testing began so we bought two more.
The second one worked. With the third, the "up" incline worked fine, but pressing the "down" button turned off power to the belt's motor and the machine coasted to a stop. Sometimes, pressing the "down" button again would turn the machine back on, and pressing the power button worked when that did not.