Using the db reconnect function

Well, if they are fetching lots of data then the connection isn't going to drop due to an inactivity timeout. Those problems typically happen when a large (really large) amount of time is spent on data processing between database calls.

I'd expect a "no connection available" (aka "cannot connect") error would be a more likely problem on a heavily used database.

Got any error log or on-screen messages you can precisely quote? That might shake loose some ideas as to the problem.