I think I see the problem here. One of the PBs is configured to run 3600 LEDs and the other is at 1800 LEDs. At those LED counts you will have vastly different FPS and with WS2812 it will be even worse. Is there a possibility for you to balance the count of LEDs? Also that is a lot of WS2812. At raw max output you’ll get pretty choppy results on any pattern.
Have you also been able to confirm that the patterns are using time()?