Valuable Articles Coverage for the Loss of Wine

We insure a wine collection under a valuable articles policy. It is an all risk policy, offering coverage against physical loss if the valuable articles are lost, damaged, or destroyed. There are several exclusions on the policy, including one for wear and tear and deterioration; this exclusion has an exception for an ensuing covered loss.

The corks in several bottles deteriorated and when the corks went bad, the wine spilled out of the bottles. We think this is a covered loss but the insurer says that the wine deteriorated as the corks went bad. What is your opinion?