Many chemicals both in the detergents and possibly in water can cause damages to the machine. There are some other problems like hosepipes or other fittings getting loosened in the course of time. Improper electrical connections can also cause damages to the machine. No one can predict the problems that may occur due to moisture, heat, chemicals and electricity. Overloading of clothes also can cause damage to the machine.
You might be wondering if it is really worthwhile buying online as there is the freight to consider. But don't forget that your bricks and mortar stores also have to pay freight on the parts they get - and they then pass that cost on to you, as well as their other overheads. By buying parts online you can often get steep discounts as online stores do not have to pay staff or rent for a shop front. And often they will give you free freight if the cost of your purchase is over a certain amount.