Iron Citadel - 1 monster remains - failed...

Hi Team,
I have completed Iron Citadel, I defeated the boss, but it still was saying 1 monster remains...
I was searching 10 times the map to find the last monster but there had no alive...
I came back to boss and I don't know but on minimap (middle of the screenshot) there was visible his "boss icon". Maybe it didn't get it?


I got from the boss his item: Ancient Crisis Fragment, however when I left the location it shows on Atlat that the map is failed...
Can you help me please?

Got the same bug for the second time in a row now..

same bug, also twice in a row

Since the release this has been bugged for almost everyone , have the same issue too