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That problem *might* perhaps be a cheap-enough fix requiring some labor, a few tools and some time.
Sometimes when a belt over-speeds briefly and then stops, the problem is that it has not sensed the speed at which the belt is moving, and has shut down for safety reasons.
And sometimes the lack of sensing the speed, is because the speed sensor, a small component that is mounted near a rotating part of the treadmill's interior parts, which rotates when the belt is moving, has slipped out of alignment a little and is no longer 'reading' the rotating element.
Would you be interested in opening up the treadmill by taking off its cover pieces, and locating the speed sensor, then testing it (possibly with a meter, possibly just by watching an LED light on one of the circuit boards) and readjusting it as necessary?
This might not turn out to actually be the problem, but it is a first thing to try in this case.