setting pitchbend for software instruments

basically i haven't set any parameters. i'm using the instrument pitchbend exactly how it comes set with garageband. it sounds great while i'm recording it, but on playback its juast a little like.....a warble? when i try to adjust it in the editori drag 2 points down to where i want the drop. then when i play it back, it only drops where the points are for maybe a second on each point, but in between it goes back to normal. i would think it should drop for the duration between the 2 points, but it doesn't.

i have discovered that when i save the project and exit, then re-enter it the pitchbend works fine. it has been suggested that i may have a glitch in my installation and to try re-installing garageband, although i have not tried this yet.