I am with him in this game and here are my info
If you need anything else just let us know, we are really having a blast with the game and would like to be able to finish it all together 
none of us are the host, we will have him post everything here real soon.
Even with the patch nothing happens when I enter the boss arena, we are in combat cause our stamina drops and there are corpse of big bats (first wave before boss) but nothing else.
Had the same issue with the Winged brood. We (full lobby of 4 players) fought it as usual, but at some point one of us decided to respawn during the boss fight and acidentally jumped down on the arena, at first we thought it was a feature, so I decided to do the same when I died. After we deafeted the first fase of the boss we got stuck. the arena opened, but the game says we’re still in the boss fight. We can tp to other locations and trade there (for example) and do whatever in other areas, but can’t progress any further in the quest.
Really hope for a fix to be realesed soon!
Love the game btw.
Hello,
We’re having the same problem with this quest in a 2-player game. After dying in the gargoyle fight, we respawned and killed the gargoyles that aggroed us outside the arena. Once they were killed, the boss never appeared, and we’re stuck at this stage of the quest. In the arena, we’re stuck as if we were in a boss fight (stamina loss, no interaction with my teammate), but nothing happens. We can’t even reach the battering ram on the wooden door.
We tried to kill ourselves in this room to reset the fight, but it didn’t work.
I hope a solution or patch comes soon to fix this. We’re enjoying playing this game 
This bug is being investigated.
My group of 3 also had this bug pop up. we’re just grinding crucible til the fix lol
I bought the game thinking this patch would fix it but it did not. still not boss winged beats spawn and i cant walk into the cave, anyway to bypass it?
Dear team,
after Boss fight( as we think we’ve completed it) we are not able to progress/climb the stone bridge. It still show us that we are in Boss fight, without any encounter. Picture added for references.
we have this exact issue on our co op run , i finished the boss when my 2 friends died and one respawned, no more enemies to fight but its stuck our progression. Hoping for a fix so we can carry on our play through
Apology for this everyone, we are looking into it.
I found a temporary solution with my friend, which we could restart the progress of the Boss Fight by
Main menu → Realm → continue from last whisper → fight the boss.
I am not sure how much my input will contribute to this topic, but my friends can now progress through the story.
cheers,
Hello,
The problem was resolved for me with this patch, thank you for your quick response! 
Best regards,
Morgul
Problem solved, thank you very much, we can enjoy this great game again !
This did not fix it for me but I had already ran around to try to fix it myself.
We are not bugged anymore as well since the new hotfix, good work to the devs with the quick fix. Thank you very much!
Yeah seems to be fixed.
When I started the boss fight “The Wicked Brood” following the story mission, the game would not end the boss fight even though I killed all the flying monsters. Below is link video proof:
DxDiag: Microsoft OneDrive
Player log file: Microsoft OneDrive
Player-Prev log file: Microsoft OneDrive
This is on update 28175 (18 Mar 26 - patch 1)
Context: Co-op of 4, two members down/respawned during “Winged Brood”, I revive 3rd party member. We two remove most “Winged Brood” from the arena.
Issue: One “Winged Brood” had its toe stuck in a wall, so we saved for last, killed it.
The boss gate stayed sealed, no one can exit/enter/ move onto Bile Wretch
everyone in arena logs out / back in.
Everyone is now outside Arena.
Arena still locked, no one may enter
One member jumps in from side, kills self, Arena is now open
Left game for 12 hrs, boss arena will not activate.
cannot end this Main Quest.
DX + 2 Logs
Hey bearbum,
I am missing your Datastore in the WeTransfer
Could you send that as well?
Check How to Properly Report Bugs! for the instructions!
Silas