If it was an old style I'd say the transmission/gearbox.   Happened to me when washing little girl dresses that I had borrowed.    Now days I'd say you need to run a "clean cycle"    They have  Tide washing machine cleaner.   Run a load with that.    Today's  soaps are not capable of getting rid of all the gunk.    You need to run a  wash cycle of the machine monthly.   I learned the hard way with my dishwasher.   Cost me a dishwasher pump.   I now try to remember to run a dishwasher cleaner through my dishwasher monthly.