Hi there,
It is possible that you have set the wrong BPM message for your MIDI clip,
or that the BPM message on the parent unit of the MIDI clip is causing the playback speed to be less than what you expect.
If the BPM of the parent container of a MIDI clip is higher than the original speed at which the MIDI was created,
it will play the MIDI at a higher speed than the original speed,
so you can check again.
Hope this helps