Assuming you WANT to use the drumrack, cotdagoo is right.
But the release of Sampler or Simpler isn't endless but maxes out at 60 seconds, and at the assigned release time the volume is down to zero, so 'fading' starts at the actual point you release the button, it only takes longer.
just drop a song into the drumrack and play it
Why would I want to play a whole song through a drumrack? Drums = one shots.
From your first post (When i drop audio into ableton - drumracks
) you're circling around the same problem: You're using drumracks for something they're not designed for.
Explore the capability of playing clips in Session View with your Launchpad Mini instead.