Go online to the Singer site....or call the 800 # on the book for help from the source....it is possible that the machine overheated with the stippling...
it may have stopped to prevent further damage. Try it again........
otherwise, the flucuating power could be a BIG problem. Is the 7442 a computerized machine??? as you know, computers do not like power that isn't steady.
Good Luck. :-) The motor may not be able to handle what you want to do with it. :)