Stone Citadel 0 monster remain unable to complete

I've found two stone citadels and couldn't complete either time.
Both times, I cleared the whole map, killed the boss, and got the fragment drops, but I was unable to complete the map.
The first time on Stone Citadel, I had a point in the atlas for a copy of a rare mob, which I removed on the second try on the Stone Citadel, but I still couldn't complete the map.
I completed the Cooper Citadel between the two stone citadels runs.
Used rare T15 maps for all citadels runs.
I have not yet found Iron Citadel to see if it happens there.

same

+1