The bug about the disappearance of the fortress

Yesterday, while mapping, I encountered a unique map (legendary map). But because my gear wasn’t good enough, I died, and afterward, the Fortress map never appeared again. So far, I’ve run about 200-300 maps, and not a single Fortress has spawned!

I’m wondering if there’s some kind of bug—maybe failing to complete a unique map affects Fortress spawns. Up to now, I’ve been grinding for over 7-8 hours straight without seeing a single Fortress map. I’d really appreciate some help with this!