Sometimes when an older unit starts to act up, rust or dust could be building up around the electronics causing the issue. I was called in to take a look at an out of order treadmill that would not start - this facility is not under a preventive maintenance plan.
After testing, it seemed that the treadmill was indicating the emergency stop switch was not properly working. It was pretty rusty. In the case of this particular light commercial grade treadmill, the emergency stop component could not be purchased separately and the entire console was going to need to be replaced in order to restore function. That would have been more expensive than this treadmill was worth and essentially marked it for disposal.
I used a solvent and abrasive wipe to clean the two magnetic surfaces. After about 10 minutes of treatment and drying time, the unit began to work with a strong startup and no signs of likelihood to fail again.
Routine preventive maintenance of fitness equipment includes an overall check for signs of wear and where applicable, dust/rust removal.