Add to Cart Problem

[harveyscoot1962]

We had installed OPC on our site that does calculation for a product and then produces add to cart button. Please see the problems we are experiencing;
1. Some products prices is set to 0 automatically when added to cart. Only the shipping cost appears. This behaviour is random, it may work if 9 sqm of the item is selected and may not work for 10. This behaviour is random for the products.
2.The cart does not itemize the purchased products, there is no way for us to know what has been bought. It sums up all product addons as 1 in the cart.

Any help and suggestion would be greatly appreciated.