Here's how I adapt such poses, load your custom character at frame 1, then the animated pose at frame 2. In the animation palette expand the body or body part list  (small triangle beside the part name) drag and select the offending key frames and delete them, when done, select the entire timeline from frame 2 to the end and drag back over frame 1. As primorge has already said some further work may be needed to adapt the pose to your character.