This problem occurred just a few days ago. When I play the first note, it sounds like the filter is turned down. If I play legato, or if the release is set to a longer time, the filter responds to its dialed setting. When I play staccato, or if I turn the release to zero, the filter sounds like it is turned down again. This happens independent of velocity or pressure.
Video demonstration: http://youtu.be/BQcGOGzNgww