I've been seeing this sporadically at least since early versions of 3.0. When switching between layer sets, particle settings sometimes don't load correctly. Just now when switching back to group A layerset 1, the particle system was much smaller than it should have been. The GUI shows the particle size knob at max value. I turned the know down and up again and the particles became the correct big size. So, when switching layersets, the GUI got updated with the correct value but the internal state was something wrong. I have also seen this with part/sec, where returning to a particle system it won't be generating at the correct rate.