Treadmill just stops?

my wife and i just bought a used treadmill its a pro form cr 610..we only paid 125 $ for it..figured we were getting a good deal,,guy claimed it had hardly been used and based on the wear of the machine he was telling the truth..when my wife walks on it it stops on her after about 1 and a half to 2 miles at 3.5 miles per hour witch is a pretty good distance..is it normal for it to just stop like that the motor gets very hot..the distance that she walks is pretty great and she weighs around 22o bless her heart she is trying to lose weight..i want to know if its normal because i am going to sell it and i am very honest dont want to rip anyone off,,need to know if i have to fix it first..i just bought a new bowflex treadclimber and its a very nice machine..thanks for ur time ..i know im alittle long winded..