Some sources continue to say that repeated vinegar use in your washer can cause damage to the rubber gaskets and such in your washer. The vinegar you can get your hands on typically contains from 5% to 8% acetic acid by volume, which is very low. You're then diluting about half a cup at most of this vinegar into liters of water and using it to clean detergent residue. When detergent and vinegar interact they neutralize each other, that's why we're using vinegar in the first place. All this places the risk of any damage beyond low in my opinion and is why so many sources can recommend vinegar as a fabric softener and not get sued.