I thought it was one of the valves based on research and conversations with LG support. After talking with APP customer service we discovered a more common cause is the filter head that the filters plug in to. I ordered the piece and it arrived quickly. Not any videos on APP website for this specific piece. Did find a paragraph describing the process in q&a. Spent about 30 mins replacing the part using only a phillips screwdriver. The most difficult part was disconnecting/reconnecting the water lines. There's not a lot of slack in the lines and I had to stretch to reach them in the top, left, back corner.