We are having issues where the original hold placed is not being placed on our server quickly enough (We have already worked with support on this and done everything they have suggested). When the user does not receive an immediate notification that the hold has been placed, they will click the place hold button again, which results in duplicate holds. We need to have some kind of lock in place while the first API call is in progress, regardless of how long that takes, as the first hold does eventually get placed and now the customer has reserved two (or more) copies. This causes a lot of work on our staff to processes these unwanted holds as users don't know to check their account immediately to see how many holds they have on on a title.
If we could even have a setting for libraries that do not want duplicate holds allowed by customers, that would be even better so libraries have a choice. The API call should check if a hold exists for that patron on both the bib and item, and not allow a new hold to be placed. The opac and Sierra have settings for this, but Discover does not.
If neither of these can be done, we would like a banner to display during the API call on the first hold request to popup and say "Please do not click the button to place a hold a second time as this may result in more than one hold". This is similar to other public websites that have this message on their payments screens to avoid people accidentally paying their fee twice if the transaction is slow.