My neighbor is selling a 2005 D1 Sarena Bay. The upper control has water condensation and is difficult to read but still works and is the spa's second unit. The heater and circ pump have also been replaced. He is offering it for $5,000, but are these problems things that tend to reoccur? I have heard some unhappy customers about their upper control with D1, I just don't want to buy something that will need extensive repair a few years later. Thanks!