I have LG washing machine that I bought when I bought my house (new in 2009) and haven't had any problems with it until this year. Now it is getting really bad water hammer during the beginning of the cycle when the solenoid is cycling really fast. I believe it is only one of the water lines--I'll have to confirm. There are surge arrestors on the faucets and the supply lines aren't super long.

Is there anything that could cause this sudden change? Solenoid going out? Air bubble somewhere in the system? Arrestor falling apart?