Placing 2 or more reverse hiding hidden zones overlapped make them no longer hide the objects inside the overlap from anyone.
In public beta (previous version), the ‘stacking’ of reversed hidden zones works as expected, hiding the objects inside them from the colors of the individual reversed hidden zones.
Example: Create 2 hidden zones with overlapping areas. Change the hidden zones to any color (2 different colors) and set both of the hidden zones to ‘Reverse Hiding.’ Then, sit in one of the colors of the hidden zones and put an object into the intersection of the 2 hidden zones. The object won’t be hidden. (I have specifically tested with regular playing cards, dice, and marbles.)
The zones hide correctly when I test it: perhaps you could provide a save file where you see the incorrect behaviour?