Jungle Valley boss not captured in Ritual Vessel

A Ritual Vessel didn't capture the boss (at least the text doesn't say it did) and that makes the Ritual Encounters V challenges impossible. Maybe it doesn't always happen, but having a Ritual spawn in the boss room is enough RNG.

The image doesn't seem to be visible. - https://imgur.com/a/Z7wh7Mt

I have been trying to capture this boss as well...

5 times ritual has spawned in the boss room.
5 times I have killed the boss within the ritual circle (once was twinned and i made sure both died within circle).
5 times I activated ritual.

5 times no boss capture....

http://puu.sh/Him5p/6a07561d88.jpg

I understand there is an element of rng involved....but ALL my other captures occurred within 1-3 tries.

Edit; I suspect the ritual just isn't respawning the boss for some reason.

Edit 2: Saw the other Jungle Valley post and followed advice to take out support gems and kill the Queen S L O W L Y. That worked.......but players shouldn't need to resort to such half-assed work-arounds.