The problem might be a true leak in the OPC Server, or it may be induced by a client, e.g. if the OPC client does not release what it should.

My guess is that independent of which of the above is the case, it shows only with QuickOPC because we automate the connections and disconnections, and with the usage pattern you described, it is likely that the connections and disconnections are made frequently.

I suggest that you first try to increase the "hold periods", I.e. amount of time the connection is kept open by QuickOPc after an operation has been performed.

You can increase the time the connection is held by setting a property in HoldPeriod, e.g. for 2 minutes:
easyDAClient.HoldPeriods.TopicRead = 2*60*1000;

and the same for the TopicWrite property.

Best regards