Distortion problem while looping in precue & mixing into a live track

I’ve recently had a recurring audio problem on my iMac while using Djay Pro. I’ve been using this software for 1 - 4 gigs almost weekly for 5 years with zero problems until now, and all on the same computer. While beat matching and looping a track in precue while a live track is playing, I will get distortions in the precued track when it loops back to the beginning of that loop (speeding up and slowing down of the track). Sometimes I will also get a quick speed up while transitioning live from the active track to the new one. I make sure no other programs are running when I use Djay Pro. It doesn’t happen after every track, but I’ve noticed that it’s more likely to happen when a track doesn’t open with a distinct, pronounced beat to match to, but even then it does happen sometimes. Thoughts? I play a lot of club gigs and even just one poor, warbling transition can sometimes mean not being asked back.

Apologies, I meant Mac Book, not iMac. Everything else was correct!