Abyss Scarabs and/or Abyss in map device not working properly

I have been using 2 Abyss Scarabs (which guarantee an additional abyss) as well as the map device Abyss option to add 2 additional abysses to my Dunes maps, but a lot of times it will only give me 1-2 abysses in the entire map. My map info says "Area contains 4 additional abysses", but I only have one or two.