Here's what I would do. I'd be afraid to void the warranty by replacing a part of the system that wasn't tested as part of the system.
So I'd keep the "defective" part and ask ESS if they'd be willing to extend the warranty on that part only. So if the system fails after the 2 year warranty and it's fails because of the part in question (and for that reason only), then they'd still warranty it as you brought it to their attention prior to the failure.
If ESS really believes this is only cosmetic, I can't see why they'd not agree to this. Also, I'd do this via email so I had written documentation. Doing this, not only would I feel confident that the part would hold up, but I'd know that ESS stands behind their product.
GOOD LUCK!
So I'd keep the "defective" part and ask ESS if they'd be willing to extend the warranty on that part only. So if the system fails after the 2 year warranty and it's fails because of the part in question (and for that reason only), then they'd still warranty it as you brought it to their attention prior to the failure.
If ESS really believes this is only cosmetic, I can't see why they'd not agree to this. Also, I'd do this via email so I had written documentation. Doing this, not only would I feel confident that the part would hold up, but I'd know that ESS stands behind their product.
GOOD LUCK!