This is not the desired behavior. I will check to see if there is any quick fix.
As for using a different tuner to such situation, it is not a good idea. Most people want to use as few tuners as possible. Imagine at one moment there is a "free" tuner to record the second show, but five minutes later that tuner is needed for a third show, on a different channel, but you have used it for the second show unnecessarily.