If Goodchild is not who you have been dealing then I suggest you take your battery to Goodchild. Show them your problem with your Optima and have a talk about whether they have seen similar, their opinion on whether it is a fault with the battery. They may be able to offer advice on dealing directly with Optima about it.
Goodchild are a large WA battery wholesaler, they deal in Optima - Goodchild Enterprises

