Missing abysses in Moon Temple

I opened a Moon Temple map with the "Fortune Favors the Brave" mod and it rolled "area contains 2 additional abysses" according to the map mods:



However, only one abyss spawned (bottom right, opened a lich!). The map also took exceptionally long to open (several seconds), so I presume the terrain generator tried hard but gave up.

Report reference number: 3871288459