Referense 3,020,306,314 - Map not completing with 0 monsters remaning

I did a level 76 Oasis map but when there were 0 monsters remaining it still didn't complete. It is a map without a map boss.

I ran the map 2 times and same problem both times.
Second time i noticed that I don't think there was a single rare monster the entire map. So maybe that caused the issue.

I did the map again now after I did another map in between, and this time it spawned rare monsters and completed.