Map mod "Abyss Pits in Area Always Have Rewards" not working

It seems like the waystone mod that gives "Abyss Pits in Area Always Have Rewards" is not always working. I use it on "areas overrun by the Abyssal" however it only works on like 90% of the pits.

I think the issue might be related to killing the map boss, since before the boss all of the pits had a chest, after killing the boss it seemed to go back to normal behaviour.

+1

Another map (Marrow) and the last three pits didn't have any rewards with the "Always have rewards" mod.