New motor will not fix the problem - this issue is something is not resetting. Motor will keep running until everything resets. Sometimes this can be a score reel - other times it can be something else. Even if score reels are resetting to zero a dirty contact might not send that signal to the score motor. EM's take some time & energy to fix!

Two things that I look at when score motors keep running are score reels and bonus steppers. The score motor keeps running in the reset sequence because something is telling it something isn't reset.

Score reels have zero position switches as do bonus steppers. You'll have to go through each score reel and run the reel by hand and watch the switches when the reel goes from 9 to 0. You'll see a switch open at 0. Make sure that switch is clean and adjusted. Same with the bonus stepper. When it's reset to the zero position there's a switch that opens, make sure that switch is clean and adjusted as well

All of the above is true. Perhaps manually set all the digits of the score reels to "0". Score reels are big culprits of NOT resetting a game.

You WILL have to clean all of them eventually, but maybe this might help you stop the score motor. Cleaning stuck items is going to be necessary.

You also might unplug the Playfield using the Jones Plugs. This might assist you to see what is causing the motor to stay spinning.

http://www.pinrepair.com/em/

Read this.