Hiya Paul, The bit of plastic you are referring to is more likely the SEAL around the washing machine. The seal is the part that goes around the door to prevent any water leaking on the floor. It is possible that the seal if it was not fixed properly could be splitting and thus being ripped apart when in operation. You can get and fix replacement seals yourself but be advised to buy long screwdrivers to replace the seal as the screws are often underneath ;or in stupid positions. Therefore using a long scredriver (Posidrive /flat) is often used) Also be careful if your replacing the seal as it is not as easy trying to place the metal ring round the seal either. You need to be sure that the seal is tight along with the securing band (metal ring) and as a tip for you, put the metal ring where you can tighten it up ;or loosen next time. NEVER PUT UNDER MACHINE !
Anthony Tovey
September 2010