I'm running on a iMac Pro (2017) Mojave OS 10.14 and using Illustrator CC 2019 v23.0. I've tried using the divide tool via the Pathfinder panel as well as the new Properties Panel and neither will work. Typically it would divide the two patterns top and bottom and now it just leaves the patterns as is without dividing. I also have used the guides to divide a pattern and that is not working either.