I have a Sears 1000LS Space Maker ModelNNN-NN-NNNNand we have issues with the belt stopping. I have replaced the motor, the motor belt, the circuit board and it still stops after running for a few min.
Replaced motor,motor belt,circuit board,
A treadmill will shut down/slow down from to much friction which is due to high motor current because the walkbelt and deck are not properly lubricated. Take an amperage reading from the motor and if it is above 10-12 amps steadily I would recommend lubricating the deck first and retest if it still cuts out replace the walking deck. Apply .5 oz of lubricant on the deck every 3-6 months or 100 hours of use. This will extend your treadmill's life many years.
Im still trying to see if the lube of the walking belt works. I should know tomorrow then I'll let you know
20+ years experience repairing exercise equipment with emphasis on Nordictrack/Proform and Horizon