Trade Center does not updates prices or diamond details based on any changes the seller makes to their general RapNet listing.
When a trade starts, the diamond details and price are frozen and shown according to when the buyer sent the Contact Seller. Both buyer and seller will see these original details in the light blue header on Trade Center.
Any changes between buyer and seller in the Trade Center are then done within the negotiation and remain private, regardless of changes the seller may make on RapNet.
Sellers should update the price in their negotiation with the buyer or use the messaging feature, both located on the Trading tab of the negotiation.