I just found a weird behaviour:
I have 5 Sliders and a Button in my plugin - when I clik on a Button parameter all the sliders change their values. When I want to go back to the previous state and choose Undo, only one slider changes its value to the previous state. I need to choose the Undo option 5 times to go back properly (I even tried the Undo Group, but it didn't work).
So I replaced a PF_ADD_BUTTON with a PF_ADD_CHECKBOX, then clicked on a Checkbox to change all the sliders, then I choose the Undo option and all the sliders went back to their previous values with one click.
Why doesn't it work for a Button parameter? Is it a known issue?