if you mean that constant "loop" that starts around 1:16, it reminds me of this:
https://www.youtube.com/watch?v=QNJL...youtu.be&t=19s
id guess P.McCartney used a sampled kit of percussions - maybe some of those hits were reversed (thats how i'd replicate this)
if you mean that short roll (pitching down) before the percussion loop starts, id say thats a drummachine snare roll, with pitchbend