Kontakt 7 locking up when setting a Crossfade value for sample

I've been using Kontakt 7 on a Macbook Pro (Monterey, 12.6.3 with M1 Pro & 32GB memory) for the past few days - importing some wav file samples of patches from my Kronos into new instruments on the Kontakt side. I haven't had any problems until today.

I've pulled in a set of samples each 15s long, some of the notes need a loop. I've selected a begin & end point. So far so good, when I try to set a crossfade value to 3000 (Which I've done with all other samples). As soon as I press enter Kontakt immediately displays the rotating beach ball and locks up, requiring a force application quit.

I've tried rebooting, making sure all other applications are closed, and also simply tried importing a single WAV file for one key to see if that helps, but the lockups continue. I tried loading the same sample into the mac mini that's part of my performance rig (Ventura 13.2.1, M2 Pro, 32GB) and the same thing happened there when I tried to apply a crossfade value.

I tried this with a shorter sample (5s) and there wasn't a problem. Is there a known problem/restriction for trying to set a crossfade for a loop long samples? Some of the sounds I sampled are synth-like with some LFO sweeps that begin after 9s, so I wanted to capture all of it. Not sure if I need to re-sample these, if so is there a different length I should target?

On some of these, I may just have to try and re-create the sound from scratch, but that takes a while, and I'm trying to debut the vst rig later this week, so sampling seemed quicker to match what I've been doing.