Unfinished Abyss

There no visible mobs to finish the abyss. I was also waiting for "underground mobs" but nothing

https://imgur.com/a/sRjVofb

Second to this, ran into this issue on multiple maps where I clear the map until it says "0 monsters remain" to try to find the missing abyss mobs but the abyss crack sits there as if I'm still missing one or two mobs somewhere... :(

Just happened to me in riverhold map.
two green dots remain and there are no mobs to kill anywhere

same

grimhaven

zero monsters remain

1248160192 reference

Same happens to me a node will collide with ritual stake or just the terrain and be uncompletable.